Since I fitted the new “8kW” diesel heater to the camping power trolley, it has occurred to me that there is a lot of energy in the exhaust gas stream that ordinarily would be wasted into the atmosphere. Since we’re all still on lockdown here in the UK, I figured it would be good to run an experiment to see if it was worth recovering this energy – in the form of heating water.
Heat Exchanger
Some time ago, I stripped an old gas combi boiler, and recovered some parts – most important here the HDW plate heat exchanger. This large chunk of stainless steel is a stack of formed plates, brazed together, that usually would heat Domestic Hot Water. In this instance it’s being repurposed to transfer heat from exhaust gas to water.
Brazed Connections
These heat exchangers are mounted in the boiler via a plate with O-Ring seals on, so they don’t really have fittings – just holes in the end plate. Solving this problem was simple – braze on some copper fittings with 55% silver brazing rod. The 22mm is the exhaust side, while the 15mm is the water side.
First Test
Cobbling together some random hose & fittings, along with a small water pump allowed me to run a first test. At this point there is no lagging at all on the exhaust system from the heater, so it’s going to shed a lot of exhaust heat into the air before it even gets to the heat exchanger. However I was able to get around 600W of heat into 15L of water, heating it up nicely. The heat exchanger is plumbed contra-flow here – exhaust comes in via the stainless tube on the bottom right, and water comes in through the speedfit elbow on the top left.
Lagged Heat Exchanger
After the temperature of the water tank hit a plateau at around 45°C, I decided to insulate everything the best I could with what I currently have. I’ve wrapped the heat exchanger with some recycled PET insulation here, just to hold the heat inside. I’m not concerned about the exhaust outlet being in contact with the fluff – this system is so effective at pulling the heat out of the exhaust that the gas exiting the far end is totally cold!
Unlagged Exhaust
Now it was time to get the exhaust system under the trolley insulated. This is the system removed from the unit entirely. This is constructed from copper pipe, brazed onto standard silencers. Deadening the sound from the unit is important, as this gets used on campsites!
Fibreglass Tape Insulation
An hour & some itchiness later, the exhaust is completely covered in fibreglass insulation, secured in place with stainless steel ties.
Exhaust Hanger
The exhaust originally passed through a close-fitting hole in the frame rail which would obviously not work now due to the thickness of the insulation layer, so this was modified with a grinder. Since there was now no support for this end of the exhaust, a pair of drilled holes & some stainless steel wire form a nice hanger!
With all this insulation in place (including around the tank & pump), the rig is now able to easily hit 65°C within a short time, so there has definitely been an improvement. At this point, it’s clear that waste heat recovery is worthwhile, so I’ll be building a proper rig to capture this energy for reuse!
It recently became rather obvious there was something amiss with the water heater on board nb Tanya Louise – lots of smoke from the exhaust, failed starts, and finally a total refusal to start altogether.
Combustion Chamber
On disassembly, it was clear the burner was the issue – above. The mesh at the back where the fuel inlet enters the burner is completely knackered. The burner in these heaters, like the Eberspachers, is evaporative. Diesel fuel is led into a high-surface area mesh tube, or pad in this case, where it is vaporized to be burned with air from the combustion blower. Initially, this heat is provided by the glow plug, but after the unit has fired, the heat of combustion keeps the process going.
Burner Deposits 1
As can be seen at left, there’s quite the build-up of solid carbon around the burner, blocking most of the mesh & the air mixing holes in the tube. This was also after I’d removed most of the fouling!
Burner Deposits 2
More deposits are seen on the other side, along with some of the air mixing holes.
Inlet Plate
Now, the problem is that these burner units are not meant to be refurbished. These units are considered by the manufacturer to be disposable, and are welded together as a result. There’s another issue – I don’t believe that a component costing around £295 in a service kit as DISPOSABLE. There’s nothing wrong with the structure of the burner at all – it’s Stainless Steel, and is in good shape with no heat damage. The only fault is with the mesh being burned out from long use. Luckily, replacement burner meshes are available on eBay from Chinese suppliers, so on with the repair! One of the welds that needs to be removed can be seen here next to the glow plug well, and there are 3 spots around the rim that are welded in this way. Delicate use of a grinding wheel on the welds allows this to be removed intact.
Burner Tube
Once the welds have been ground off, the fuel inlet plate with the mesh can be pulled from the back of the burner. It’s a good idea to add some registration marks to both pieces before they’re separated, so they can be put back together in the same orientation – required for both the glow plug wiring, and the fuel inlet tube to line up with the hole in the heater housing. The ring of slots visible around the edge of the tube are the combustion air inlets, and the air is directed through a ring of holes in the combustion chamber, quite similar to a turbine engine combustor.
Old Burner Mesh
Now I’ve got the back of the burner removed, the clogging is much easier to see. The mesh itself has clearly been subject to very high heat, and is partially burned away, along with most of the surface being clogged up with coal from incomplete combustion. It’s difficult to see here, but the mesh pad is held in place with a large circlip around the edge, all will become clear after cleaning. All the hard carbon needs to be scraped out of the cup, clearing the way for the clip to be pried out of it’s groove.
Cleaned Cup
After a lot of scraping with the sharp end of a small screwdriver, the cup has been relieved of enough carbon to be recognisable again! The fuel inlet tube is in the centre of the backplate, with the circlip groove around the edge. Crimp marks are visible on the top edge of the groove – I think Webasto actually crimps the ring in place after fitting, which does make removal a bit more tricky, but I did manage to get it out intact, even if heat has removed most of the heat treat from the steel – making it soft. Be careful here!
New Mesh Fitted
Fitting the new mesh is pretty simple. These have a sharp pressed side & a convex side, the convex side must face outwards from the cup. The circlip is visible around the edge of the mesh, with the ends next to the glow plug well. Make sure that the clip is equally spaced around the glow plug to make sure it doesn’t foul the plug when that’s replaced.
Now comes the issue of reattaching the cup to the back of the burner tube. I didn’t want to re-weld, since the assembly is Stainless Steel & I don’t have a TIG setup at present. I do have some stainless wire for the MIG, but this would also leave me with the issue of future disassembly if the mesh needs replacement again. Brazing is also not possible for the same reason – once brazed, it’s a permanent assembly.
Burner Reassembled
Since there are some tabs that were never welded, I decided to drill & tap M2.5 through these & use 304 stainless screws to hold the components together. This should allow removal in the future if required.
While I’m pretty happy with the Chinese diesel heater replacement for the old Eberspacher on the trolley, the stock controller leaves much to be desired. While functional, it’s fairly unresponsive, bulky & doesn’t allow external control as the Eberspacher did with it’s simple ON/OFF signal. So after a massive amount of searching on the web, (it wasn’t easy to find, damn SEO!), I discovered a project by a chap in Australia who has reverse engineered the communications protocol of these heaters, & built a fully custom controller. This is based around the ESP32 Wi-Fi microcontroller, and a Bluetooth HC-05 module. Display is by means of a 1.3″ OLED screen.
Bare PCB
Here’s the bare PCB kindly sent to me by Ray down under to get this project kickstarted. No THT components here apart from headers, everything is minimum 0805 size.
Populated PCB
Here’s the controller PCB fully populated, with the ESP32 & Bluetooth HC-05 modules on board. There was a slight issue with the 3.3v regulator not matching the pinout of the PCB, so some minor bodge work required there, but the current draw of the unit is so low that the regulator doesn’t get warm, even with the heatsink tab floating in mid-air. I’ll hot-snot this down to avoid any vibration issues. Incedentally, soldering the castellated connections of the modules is a real pain – problems with contacts not wetting first time were an issue here. Use plenty of flux!
The two JST connectors are for the main heater loom, and an external temperature probe that feeds back for the thermostat mode of the controller. Reset & Bootloader buttons are provided on the board for easy firmware loading. There’s also some spare GPIO broken out for other uses, along with the required UART port for firmware & debugging access. The clock is maintained by a DS3231 RTC IC, which oddly enough is expensive on it’s own – buying an Arduino RTC module & using a hot-air pencil to desolder the IC worked out £4 cheaper than buying the IC direct! The RTC is backed up by a lithium coin cell.
The communications interface is taken care of by a couple of single gates in SOT-23 packages, which interfaces the 3v3 ESP32 with the 5v signalling levels of the heater’s control bus. This unit is a little odd for a communications interface – it is standard serial, but at an odd baud rate of 25,000, and instead of separate TX & RX lines, the transmissions are gated for TX & RX down a single wire. I fail to understand the logic of doing this, since wire isn’t expensive & extra components just add complexity!
A couple of build notes on this controller:
R4 & R5 are swapped on the silkscreen. Bootloader issues ensued!
The blue PCB Bluetooth module doesn’t function correctly with the controller, allowing receive but no transmit. Odd.
There are two pinout variations on the 1.3″ OLEDs. This layout requires the GND pin leftmost.
PCB Front
The front of the PCB holds the OLED display panel, and the control button array. Not much else on this side of the board besides the RTC battery switching diodes & some passives.
Glow Plug Heating
The case to house the PCB is 3D printed, I didn’t bother with the matching buttons as I don’t currently have any flexible filament to print with, so long stem tact switches are used. The controller is running the heater through a cycle here on the Detailed Info screen, where the most comprehensive heater info is displayed. In this stage, the heater’s ECU is warming the glow plug up ready for ignition.
Igniting
After the glow plug has heated, the ECU starts the fuel metering pump at it’s lowest rate to get a flame going. The glow plug is still active to vaporise the fuel.
Burner Running – Heatup
Once the thermistor on the heat exchanger registers a temperature increase, the ECU detects the burner has lit, and starts increasing the fuelling rate & blower speed.
Warming Up
Once the temperature hits a threshold, around 55°C, the ECU switches off the glow plug & ramps the fuelling rate up to max to warm the heat exchanger to operating temperature. The detailed page displays both the room temperature (left), set temperature & heat exchanger temperature (right).
Heater Running
Once the heat exchanger has reached running temperature, the ECU switches control to the thermostat, in this case the new controller.
Shutdown
When a shutdown is initiated, the heater brings the glow plug back on & reduces the fuelling rate to minimum for a couple of minutes, before stopping fuel flow. The glow plug remains running for a while to burn off any remaining fuel residue.
Cooling Cycle
Finally, the ECU cuts power to the glow plug, and keeps the fan running at medium speed until the heat exchanger cools to below 55°C.
As part of the giant power bank that gets dragged to all my major camping trips & festivals, there is an old Eberspacher Diesel heater, a D1LCC from at first guess somewhere in the mid 90’s. At only 1.8kW heat output this is a little small for our current tent, and it struggles to keep the temperature comfortable at night, so with Chinese clones on the market these days much cheaper than the Eberspacher or Webasto units, a replacement was up! Still, the old Eberspacher is in working order, and will probably get used for some other project.
Diesel Heaters
After removing the old D1LCC & placing it next to the new one, the size difference is obvious! The new heater is a Chinese clone of the Eberspacher D4 unit, allegedly uprated to 8kW. (In reality, it’s probably around 5kW heat output at full tilt). Luckily, it’s not that much larger than the old one, so it’ll go into the same space.
New Heater
The port layout on the bottom of the heater is identical apart from intake port size, a quick attack of the baseplate with a grinder to remove the old hole pattern allowed the supplied mounting plate to fit correctly into place for the new heater. The duct size on this unit is also bigger than the old 60mm – 75mm duct is used on these large units. No modification to the vent hole was required, as the 75mm vent already fit perfectly. To clear the fittings on the top of the fuel tank, which is just underneath the hot air exhaust cowling of the heater, the mounting plate is fixed using 10mm nylon standoffs, this also helps get a bit more natural airflow around the base of the heater, as the mounting gets to 90°C in operation at full power!
These heaters don’t use the Eberspacher standard switch wire for control – there are only 3 pins in the loom to the controller, for 5v power & an odd UART which uses gated TX/RX to avoid having a separate line for each.
Stock Controller
The stock controller has quite a nice looking LCD display, but it’s less than responsive & the backlight is always on at full tilt. It’s also much larger than the Eberspacher 701 controller so would require some rejigging of the control panel on the trolley. The built-in thermostat is also inaccurate, being almost 5°C high no matter what the room temperature. Ray Jones from Down Under has designed an open source ESP32 based controller for these heaters, and one of these is currently being built to control the unit. More to come on this bit!
Stock Controller PCB
A quick teardown of the controller reveals pretty simple internals, there’s a microcontroller, probably an STM8 device by looking at the programming header, but the markings have been scrubbed off the IC. There’s a standard LCD controller IC, a RTC which isn’t battery backed, and a 433MHz receiver IC with PCB trace antenna.
I wasn’t able to get the remote control function working with any of the remotes I have, any attempt at pairing a remote didn’t give any response from the controller unit. I also tried a 315MHz remote, but that didn’t work either. Not an issue since I’m building a much better open source controller.
Fuel & Exhaust
Under the base is the exhaust system & the fuel dosing pump. There’s a small filter in the feed line from the tank to keep crap out of the pump, and nylon fuel line then runs the fuel to the heater inlet. The exhaust is made as gas-tight as possible with foil tape & exhaust paste, to keep the exhaust fumes contained in the pipework until they’re vented outside. The rest of the exhaust after the right hand silencer is done in brazed 22mm copper pipe, and a piece of Eberspacher exhaust duct is removable from the final exhaust tail for storage. The black pipe is the combustion air intake, which is simply fed into a silencer cable tied to the trolley frame.
Heater Ports
The 3 ports are visible under the mounting plate, the square hole cut out of the trolley base to accommodate everything.
Since I do festivals every year, along with a couple of other camping trips if the weather is good enough, I’ve been taking equipment with me for years in flight cases to make things more comfortable. Things like a large battery to power lights & device charging, an old Eberspacher diesel heater for the times when the weather isn’t great, and an inverter to run the pumps built into airbeds.
Red Diesel / Heating Oil is my fuel of choice for camping purposes, as it’s about the safest fuel around, unlike Butane/LPG it is not explosive, will not burn very readily unless it’s atomized properly & it’s very cheap. Paraffin is an alternative fuel, but it’s expensive in the UK, at about £12 per 5L.
The Hexamine-based tablet fuels the UK festivals promote is nasty stuff, and the resulting combustion products are nastier still. (Things like Hydrogen Cyanide, Formaldehyde, Ammonia, NOX). They also leave a sticky black grok on every cooking pot that’s damn near impossible to remove. Meths / Trangia stoves are perfectly usable, but the flame is totally invisible, and the flammability of alcohol has always made me nervous when you’ve got a small pot of the stuff boiling while it’s in operation in the middle of a campsite filled with sloshed festival goers. A single well-placed kick could start a massive fire.
Previous System
Over the years the gear has evolved and grown in size, so I decided building everything into one unit on wheels would be the best way forward. I’ve been working on this for some time, so it’s time to get some of the details on the blog! Above you can see the system used for last year’s camping, the heater is separate, with a 25L drum of heating oil, the battery is underneath the flight case containing all the power components, and it’s currently charging All The Things.
Overview
Above is the new unit almost finished, the bottom frame is a standard eBay-grade 4-wheel trolley with a few modifications of my own, with a new top box built from 12mm hardwood marine plywood. This top is secured in place with coach bolts through the 25mm angle iron of the trolley base. The essential carbon monoxide detector is fitted at the corner.
Internal View
The inside gets a bit busy with everything crammed in. The large Yuasa 200Ah lead-acid battery is at the far end, with it’s isolation switch. Right in the middle is the Eberspacher heater with it’s hot air ducting. I’ve fitted my usual 12/24v dual voltage system here, with the 24v rail generated from a large 1200W DC-DC converter.
Heater Vent
The hot air duct for the heater is fed out through a standard vent in the front. Very handy for drying out after a wet day.
Main Bus Bars & Solar Controller
Here’s a closeup of the distribution bus bars, with both negative rails tied together in the centre to keep the positives as far away from each other as possible, to reduce the possibility of a short circuit between the two when working on the wiring. The EpEver Tracer 4210A MPPT Solar Charge Controller is on the left, tucked into the corner. This controller implements the main circuit protection for the battery, having a 40A limit. Individual circuits are separately fused where required. Solar input on this unit is going to be initially provided by a pair of 100W flexible panels in series for a 48v solar bus, the flexible panels are essential here as most of the festivals I attend do not allow glass of any kind onsite, not to mention the weight of rigid panels is a pain.
DC Output Sockets
I’ve stuck with the 3-pin XLR plugs for power in this design, giving both the 12v rail, 24v rail & ground.
Inverter Outputs
Tucked under the DC outputs are a pair of panel sockets for the 600W inverter. This cheapo Maplin unit is only usually used to pump up air beds, so I’m not expecting anyone to pull anything near max output, but a warning label always helps.
Power Socket Wiring
Behind the front panel is the hardwiring for the power sockets. The DC jacks are connected together using 2mm solid copper wire, bent into bus bars.The mains wiring underneath is a simple radial circuit straight from the inverter. The large cylinder on the left is a hydraulic pump from a BMW Z3, which runs a hydraulic cylinder for lifting the lid of the top box, used simply because I had one in the box of junk.
Fuel Pump
External fuelling is dealt with by a small gear pump, this is used to fuel up the Optimus Stove & Petromax Lantern. This is in fact a car windscreen wash pump, but it has coped well with pumping hydrocarbons, it currently has a small leak on the hose connections, but the seals are still entirely intact.
Remote Relays
There’s a small remote relay module here, for switching the DC output for lighting & the heater from afar. Very useful when it’s dark, since there’s no need to fumble around looking for a light switch. A car-style fob on my keyring instead.
Heater Timer
Since the Eberspacher 701 controller I have is an ex-BT version, it’s very limited in it’s on time, a separate timeswitch is fitted to control the heater automatically. Being able to return to a nice warm tent is always a bonus.
Just to the left can be seen the top ball joint for the hydraulic cylinder that lifts the top of the box.
Battery Charger
The final large component is the battery charger. This unit will maintain the battery when the trolley isn’t being used.
Router Motherboard
On the left side is the old Atom motherbaord used to provide a 4G router system. This unit gets it’s internet feed from a UMTS dongle & provides a local WiFi network for high speed connectivity. The bottom of the hydraulic cylinder is visible in the bottom right corner.
Fuel Tank Completed
Since the Eberspacher obviously needs fuel, a tank was required. In previous years I’ve used jerry cans for this purpose, but this trolley is supposed to have everything onboard, for less setup time. The tank is constructed from 3mm steel plate, MIG welded together at the seams to create a ~40L capacity. The filler neck is an eBay purchase in Stainless Steel. No photos of the tank being welded together, as I was aiming to beat sunset & it’s very difficult to operate a camera with welding gauntlets on 😉
The tank is the same width as the trolley frame, so some modification was required, having the wheels welded directly to the sides of the tank. This makes the track wider at the rear, increasing stability.
Fuel Dip Tubes
A quick view inside the tank through the level sender port shows the copper dip tubes for fuel supply to the heater, and an external fuel hose for my other fuel-powered camping gear. These tubes stop about 10mm from the bottom of the tank to stop any moisture or dirt from being drawn into the pumps.
Fuel Feeds & Level Sender Port
The top of the tank is drilled for the fuel fittings & the level sender and has already been painted here. The 1mm base plate has yet to be painted.
Level Sender Installed
Touching up the paint & fitting the sender is the last job for this part. The mesh bottom of the trolley has been replaced by a 1mm steel sheet to support the other parts, mainly the heater. Fuel lines are run in polyurethane tubing to the fuel pumps.
All the instruments & controls are on a single panel, with the Eberspacher thermostat, external fuelling port & pump switch, inverter control, the solar controller monitor panel, cover buttons, router controls, compressed air & fuel gauges.
Panel Wiring
As is usual behind instrument panels, there’s a rat’s nest of wiring. There’s still the pressure gauge to connect up for the compressed air system, and the nut on one of the router buttons is such a tight fit I’ve not managed to get it into place yet.
Eberspacher Fuel Pump
The support components for the Eberspacher heater are mounted underneath the baseplate, with the fuel dosing pump secured to a rail with a pair of cable ties, and some foam tape around to isolate the constant clicking noise these pumps create in operation. The large black cylinder is the combustion air intake silencer, with the stainless steel exhaust pipe to the left of that. Silencing these heaters is essential – they sound like a jet engine without anything to deaden the noise. Most of this is generated from the side-channel blower used in the burner.
Eberspacher Exhaust
Bolted to the underside are a pair of exhaust silencers, one is an Eberspacher brand, the other is Webasto, since the latter type are better at reducing the exhaust noise. Connections are sealed with commerical exhaust assembly paste, the usual clamps supplied do not do a good enough job of stopping exhaust leaks.
Next update to come when I get the parts in for the air compressor system.
As I mentioned in the previous post, these heaters have a standard interface that’s used for control & diagnostics, the W-Bus. This is transmitted over the K-Line of the vehicle bus, and all heaters, regardless of firmware modifications done by the various car manufacturers respond to this interface. Official Webasto diagnostic adaptors are available, but these are just a very expensive serial adaptor. A much cheaper option is a ~£5 Universal ODB adaptor.
ODB2
Above shows the signals on the ODB connector – the ones we’re interested in here are Pin 16, the +12v supply, and Pin 7, K-Line. Connect Pin 16 to the positive supply to the heater, and Pin 7 to Pin 2 on the Webasto heater. (Valid for all TT-V heaters).
Device Selection
Once these two connections are made to the heater, fire up the Thermo Test software. The screen above will be displayed. Pick W-Bus at top left.
COM Port Selection
First thing, connect the ODB adaptor to USB, and change to the correct COM port in Thermo Test. There may be several in the list, but a newly connected USB device should show up with the highest COM number.
Thermo Test
Once Thermo Test is running, start communications by going to the Diagnosis Menu > Start Diagnostic (F2 keyboard shortcut).
Initialized
After a few seconds, communication will be established. This will show faults, if any are present, and allow testing of the heater & it’s component parts. A summary report can be generated with Diagnosis > View Summary:
This shows all the important stuff, including running hours. (5388Hrs on this heater!). Most importantly, there are no faults listed.
Heater Running
The heater can be fully tested by issuing a start command from the Command Menu > Parking Heating option. Obviously cooling water will be required for this, along with an external water pump. (The water pump control output on these heaters seems to be totally disabled in firmware, as they rely on the engine’s coolant pump). I used a bucket of water along with a small centrifugal pump to provide the cooling. During this test I noted that the firmware is much more aggressive in these units. The marine versions shut down at ~72°C water temperature, whereas these don’t so the same until ~90°C.
Now I’ve managed to communicate with the heater, I’ll get onto building a standalone controller so I can dispense with the Windows VM for control.
Here’s another Diesel-fired heater related project – these Webasto heaters are fitted to Jaguar S-Type cars as auxiliary heaters, since (according to the Jag manual), the modern fuel-efficient diesels produce so little waste heat that extra help is required to run the car’s climate control system. (Although this seems to nullify any fuel efficiency boost, as the fuel saved by not producing so much waste heat in the engine itself is burned in an aux heater to provide heat anyway). The unfortunate part is these units don’t respond to applying +12v to Pin 1 of the ECU to get them to start – they are programmed to respond to CAN Bus & K-Line Bus only, so they require a bit more effort to get going. They also don’t have a built-in water circulation pump unlike the Webasto Thermo Top C heaters – they expect the water flow to be taken care of by the engine’s coolant pump.
Webasto LabelWater Side
The water ports are on the side of this heater instead of the end, the heat exhanger is on the left. These hearers are fitted to the car under the left front wing, behind a splash guard. Pretty easy to get to but they get exposed to all the road dirt, water & salt so corrosion is a little problem. The fuel dosing pump is in a much more difficult spot to get at – it’s under the car next to the fuel tank on the right hand side. Access to the underside with stands is required to get at this.
ECU Side
The ECU side has all the other connections – Combustion air, exhaust, fuel, power & control.
External Connectors
Only two of the external connectors are used on these heaters, the large two pin one is for main power – heavy cable required here as the current draw can climb to ~30A on startup while the glow plug fires. The 8-pin connector on the left is the control connector, where the CAN / K-Line / W-Bus buses live. The fuel dosing pump is also supplied from a pin on this connector. The small 3-pin under that is a blank for a circulation pump where fitted. Pinouts are here:
Pin
Signal
1
Battery Positive
2
Battery Negative
Pin Number
Signal
Notes
1
Telestart / Heater Enable
Would usually start the heater with a simple +12v ON signal, but is disabled in these heaters.
2
W-Bus / K-Line
Diagnostic Serial Bus Or Webasto Type 1533 Programmer / Clock
3
External Temp Sensor
4
CAN-
CAN Bus Low
5
Fuel Dosing Pump
Fuel Pump output. Connect pump to this pin & ground. Polarity unimportant.
6
Solenoid Valve
Fuel cutoff solenoid optionally fitted here.
7
CAN+
CAN Bus High
8
Cabin Heater Fan Control
This output switches on when heater reaches +50°C to control car heater blower
Pin
Signal
Notes
1
?
?
2
Circulation Pump +
3
Circulation Pump -
ECU Cover Removed
Removing the clipped-on plastic cover reveals the other ECU connectors. The large white one feeds the glow plug, & the large multi-pin below brings in the temp & overheat sensor signals.
MC9S12DT128B Microcontroller
The heart of the ECU is a massive microcontroller, a Freescale MC9S12DT128B, attached to a daughterboard hooked into the ECU power board.
Power Section
The high power section is on the board just under the connectors, here all the large semiconductors live for switching the fan motor, glow plug, external loads, etc.
LIN & CAN Bus Transceivers
The bus transceivers are separate ICs on the control board, a TJA1041 takes care of the CAN bus. There’s also a TJA1020 LIN bus transceiver here, which is confusing since none of the Webasto documentation mentions LIN bus control.
Combustion Fan Motor
The combustion fan motor is in the ECU compartment, nicely sealed away from the elements. There is no speed sensor on these blowers, unlike the Eberspacher ones.
Motor Details
The motor is a Buhler, rated at 10.5v.
Water Ports & Combustion Fan Cover
Unclipping the cover from the other end reveals the combustion fan, it’s under the black cover. (These are side-channel blowers, to provide the relatively high static pressure required to run the burner).
Sensor Clip
The overheat & temperature sensors are on the end of the heat exchanger, retained by a stainless clip.
Temp & Overheat Sensors
With the clip removed, the sensors can be seen better. There’s some pretty bad corrosion of the aluminium alloy on the end sensor, it’s seized in place.
Burner
The heater splits in half to reveal the evaporative burner itself. I’ve already cleaned the black crud off with a wire brush here, doesn’t look like this heater has seen much use as it’s pretty clean inside.
Burner Chamber
Inside the burner the fuel evaporates & is ignited. There is a brass mesh behind the backplate of the burner to assist with vaporisation.
Glow Plug
The glow plug is fitted into the side of the burner ceramic here. This is probably a Silicon Carbide device. It also acts as a flame sensor when the heater has fired up. The fuel inlet line is to the left under the clamp.
Heat Exhanger
The hot gases from the burner flow into the heat exchanger here, with many fins to increase the surface area. There’s only a couple of mm coating of carbon here, after 10 years on the car I would have expected it to be much more clogged.
I’m currently waiting on some components to build an interface so I can get the Webasto Thermo Test software to talk to the heater. Once this is done I can see if there are any faults logged that need sorting before I can get this heater running, but from the current state it seems to be pretty good visually. More to come once parts arrive!
The full service manual for these heaters can be grabbed from here, along with the wiring details for the Jaguar implementation & the Thermo Test software for talking to them:
Some time ago I did a couple of posts on cheapening up the maintenance of Eberspacher hot air heaters by making the glow plug screens myself. Now one of my pieces of stainless mesh has been in the heater for nearly a year, and the heater is starting to get a bit smoky on a cold start. This is usually a sign that the screen isn’t allowing the fuel to vaporise quick enough for the glow plug to ignite the flame, because it’s becoming blocked. So far the heater has had about 150L of diesel through it with my DIY screen.
Old Screen
After removing the plug, here’s what’s left of the screen. The bottom end has completely disintegrated, but this is to be expected – OEM screens do the same thing as this end is exposed to the most heat in the burner. There’s quite a bit of coke buildup on the top end of the screen around the fuel nozzle, again this isn’t surprising, as this is the coolest part of the heater not all the heavier fractions of the diesel fuel have the chance to vaporise.
Innards
Looking further down into the mixing tube of the main burner, everything looks good. There’s a coating of soot in there, but no tar-like build up that would tell me the unit isn’t burning properly. Another advantage of making my own screens is that they’re much easier to extract from the hole once they’ve been in there for months. The OEM screens have a stainless ring spot welded to the mesh itself to hold it’s shape, and once there’s enough fuel residue built up the entire mess seizes in place, requiring some sharp pokey tools & some colourful language to remove. The single loop of mesh held in place by it’s own spring pressure is much easier to remove as it collapses easily.
New 80 Mesh Screen
I’ve decided to change the mesh size of the screen while I’m in here, in this case to 80 mesh, which is much closer to the OEM screen size. There doesn’t seem to be much of a difference so far in either the starting or running capability of the heater, although the thicker wire of this screen might last longer before disintegrating at the burner end.
A while ago I posted about the glowplug screens in Eberspacher heaters, and making some DIY ones, as the OEM parts are hideously expensive for a piece of stainless mesh (£13).
Old Screen
Above is the old factory screen that I extracted after only 5 gallons of diesel was run through it, it’s heavily clogged up with carbon & tar. The result of this clogging is a rather slow & smoky start of the heater & surging of the burner while at full power.
It wasn’t as badly stuck in the chamber as some I’ve removed, but extracting it still caused the steel ring to deform, this was after using a scalpel blade to scrape the carbon off the rim.
At the time I did some tests with some spare copper mesh I had to hand, but the problem with copper is that it’s very soft & malleable, so didn’t really hold it’s shape well enough. The factory screens are spot welded to keep them in shape, but as I don’t have a spot welder, I am relying on the mesh having a bit of springiness to keep it in place against the walls of the glowplug chamber.
eBay provided a piece of 120 mesh stainless steel mesh, 300mmx300mm for £8. It’s a bit finer than the stock stuff, but appears to work perfectly fine as long as there’s no gunk in the fuel to clog it up.
I cut a strip off the large piece, as wide as the OEM screen, about 32mm. This 300mm long strip is then cut into 4 pieces, each 75mm long. (it’s easily cut with scissors, but mind the stray wires on the edges! They’re very sharp & penetrate skin easily!).
Mesh Screen
These pieces are just the right size to form a complete loop in the glowplug chamber, and the stainless is springy enough so that it doesn’t deform & become loose.
The OEM screen is multiple turns of a more coarse mesh, but the finer mesh size of the screens I’m using means only one turn is required. Multiple turns would probably be too restrictive to fuel flow.
With one of these pieces of mesh in place, the heater starts instantly, without even a wisp of smoke from the exhaust. Burner surging is also eliminated. Even if the service life of my DIY replacement isn’t as long as an OEM screen, the low price for such a large number of replacements certainly offsets that disadvantage!
A piece of mesh from eBay would provide enough material for quite a lot of replacements, and probably more than the service life of the burner itself!
One of the central parts to the Eberspacher-type evaporative burner is the wire mesh screen that surrounds the glowplug, where the incoming fuel is heated to vapour before it’s blown into the combustion chamber & burned.
These screens, like glowplugs in the older heaters, are consumable parts and either get clogged with soot/tar or just eventually burn away.
The problem is that these parts (for what they are at least) are bloody expensive, so I’ve been looking to come up with something that can serve as a decent replacement for much lower cost.
OEM Screen
Here’s a slightly used screen from my D1LCC heater, as can be seen the lower edge is already burning away even after only a few hours use. This edge tends to burn as the screen projects into the combustion chamber by about 1/4″, so it’s exposed to higher temperatures there. The rest of the screen is covered by the alloy casting that holds the burner. The mesh itself is stainless steel, and looks like something between 120-150 mesh.
The mesh is wound 2-3 turns, and spot welded to hold everything together. I would imagine to give more surface area for fuel vaporization. An unfortunate side effect of this is that the screen is much more susceptible to clogging as the mesh size is effectively reduced.
This also makes them damn near impossible to clean, as the carbon deposits get stuck between the layers in the screen. Applying a blowtorch flame to the entire screen & heating it to orange heat (~1200°C) does burn most of the crap out of them. Running Paraffin/Kerosene as the fuel also makes for a much cleaner burn, extending life.
(Assuming of course that the screen can be removed without totally destroying it – in my experience after many hours of running they seize in place & require sharp implements, violence & much swearing to remove, in several pieces.)
I had some copper mesh spare from a previous project, around the correct mesh size, so I figured I’d cut a piece to the same size as the official mesh & give it a go in the heater.
DIY Screen
Here’s my single-layer DIY screen after a couple of hours operation in the heater. Ignition time doesn’t seem to be impaired, there’s no smoke from the exhaust, and it appears that it’s staying cleaner than an OEM screen, since the mesh size is a little larger. I’ll have to monitor the situation & see how long these last, but if it’s anything close to the OEM screen life it’ll make maintenance much cheaper.
Fuel Inlet
This is the opening that holds the glowplug & it’s screen. The fuel inlet can be seen on the left wall of the chamber, with a circular groove that feeds fuel onto the screen in operation.
DIY Screen Fitted
And here’s the DIY screen in place, it’s obviously not as good a fit as the OEM version, but it’s sufficient to do the job!
Glowplug
Finally, here’s the glowplug itself. Possibly the beefiest plug I’ve ever seen, even in large diesel engines.
I go camping on a regular basis here in the UK, and often even in summer it’s horribly cold at night in a field somewhere in the middle of Leicestershire. This doesn’t go too well with my severe aversion to being cold.
For the past several years I’ve used a Tilley lamp for some heat & light while at festivals & general camping, but it’s heat output is less than stellar when used in a 6-man tent.
An Eberspacher diesel heater was what was required for the job. Above is the unit as it’s built at the moment – I’ve used an old D1LCC 1.8kW heater that was recently decommissioned from nb Tanya Louise, as it’s getting a bit funny about what kind of fuel it’ll run on in it’s old age. It’ll work perfectly well on kerosene though – a fuel I already take with me camping for the Tilley.
It’s mounted on a base box, which is a repurposed steel electrical junction box that saw a previous life containing a 3-phase fan motor controller.
Data Plate
Here’s the info on the heater unit itself. Drawing 22W of power at 12v I’ll be getting 1.8kW of heat output – sounds good to me.
Box Internals
Here’s a view into the base box before the circulation fans were fitted, in early prototype stage. I used a small toroid as a clunk on the end of the rubber fuel line 😉
Support Components
After a few bits from the Great eBay arrived, here’s the internals of the base unit at present. The fuel tank is a repurposed 2L fridge water container – made of tough HDPE so it’s fuel resistant.
The fuel pump is mounted on the left side next to the tank – having been wrapped in some foam to deaden the continual ticking noise it creates. The exhaust & it’s silencer are mounted at the rear, the silencer being retained by a surplus rubber shock mount. Luckily the exhaust systems on these heaters don’t get particularly hot, so the rubber doesn’t melt.
The exhaust outlet is routed through the frame, to be attached to an external hose. I don’t want combustion gases in the tent with me!
Standard Eberspacher silencers also aren’t gas-tight from the factory – they’re designed to be used in the open on the underframe of a vehicle, so I’ve covered all the seams in aluminium tape to make the system airtight.
Ventilation
To make sure that the support components don’t get overheated with the exhaust being in such close proximity, and to pull a little more heat out of the system, a pair of slow-running 80mm fans has been fitted to the end of the box. These blow enough air through to give a nice warm breeze from the vents on the other end of the base.
Fuel Tank
The tank I’ve used just so happened to be the perfect size to fit into the base box, and to tap the fuel off a bulkhead fitting was put into the top of the tank, with a dip tube on the other side. The fuel line itself is tiny – only 4mm.
If the specifications from Eberspacher are to be believed, 2L of fuel on board will allow the system to run for about 8 hours on full power, or 16 hours on minimum power.
Being inside the base, refuelling is a little awkward at the moment, the heater has to completely cool before the exhaust can be detached without receiving a burn, so I’ll be building in a fuel transfer system from an external jerry can later to automate the process – this will also help to avoid messy fuel spills.
More to come when the rest of the system is worked out!
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