I found last year that my FBH doesn't work so I decided I would sort it when the weather warmed up and then of course I didn't do anything about it!

Last weekend I removed it and a friend of mine made a straight coupler for me from some brass stock on his lathe so that I could plumb it out for a while.

Beautiful isn't it?


The fault I have is "Glow plug short circuit to ground or open circuit" which I had researched and found that it can be faulty or the transistor can be a culprit but when I removed the heater and put a meter on the glow plug wiring I had a dead short so I decided to just bite the bullet and order the full service kit (about £105) including the glow plug which is the expensive bit and service the FBH properly. I stripped it down to find that it was actually really clean inside, of course the gaskets were ruined but I knew they would be so I cleaned it all out and got ready to rebuild it.

Curiosity got the better of me at this point so I tested the new glow plug with my meter and found I had about 0.3ohm resistance from memory, I checked the old one, it was the same... bugger! I shoved 12v up the old glow plug wiring and it worked a treat. Double bugger!

Ah well, I've bought the stuff now and opened the packet, I may as well go ahead so I rebuilt the FBH with all the new parts. I thought for a while about the pros and cons of refitting to test but decided to give it a go at lunchtime anyway as the sun was shining on that side of the car. Yeah, it didn't work! It did briefly attempt to start the cycle but then powered down again so I decided to plug in my GapIID to see what issue I had now expecting it to be the same.

To say that Gap was inconclusive is an understatement, according to it, I have every single component of my L322 in fault and I am not joking, it started with 40 ABS module faults, every part of the HVAC, transfer case, Instrument cluster, you name it! I cannot stress enough how bad it is according to GAP. I can clear them all and every single one comes straight back and they are all dated 13/5/2023. I gave up on that, I'll charge the battery as it only does short runs currently and revisit that issue another time so lets park that there for a moment.

Back to the FBH, Can anyone recommend a company that can test it for me or is anyone local is to Maidstone that I can bring it to for a look? I found Robinsonlabs website and videos, but I've emailed them and they haven't responded, they also don't have a phone number so I'm a bit sceptical about paying £70 and posting the circuit board in case they are no longer trading.

If it's the glow plug transistor at fault, I'd fairly happily replace it myself but I'm not good enough with electronics to know that I am testing it correctly and I don't have the diagnostic capabilities for this board so it would be guess work and that's not much good to me. Usually the transistor would have damage on it to see when they burn out and as you can see in this pic, mine looks to be in perfect health (I accept that looking like it and doing it are two very different things).

Blob said:

I found last year that my FBH doesn't work so I decided I would sort it when the weather warmed up and then of course I didn't do anything about it!

Last weekend I removed it and a friend of mine made a straight coupler for me from some brass stock on his lathe so that I could plumb it out for a while.

Beautiful isn't it?

The fault I have is "Glow plug short circuit to ground or open circuit" which I had researched and found that it can be faulty or the transistor can be a culprit but when I removed the heater and put a meter on the glow plug wiring I had a dead short so I decided to just bite the bullet and order the full service kit (about £105) including the glow plug which is the expensive bit and service the FBH properly. I stripped it down to find that it was actually really clean inside, of course the gaskets were ruined but I knew they would be so I cleaned it all out and got ready to rebuild it.

Curiosity got the better of me at this point so I tested the new glow plug with my meter and found I had about 0.3ohm resistance from memory, I checked the old one, it was the same... bugger! I shoved 12v up the old glow plug wiring and it worked a treat. Double bugger!

Ah well, I've bought the stuff now and opened the packet, I may as well go ahead so I rebuilt the FBH with all the new parts. I thought for a while about the pros and cons of refitting to test but decided to give it a go at lunchtime anyway as the sun was shining on that side of the car. Yeah, it didn't work! It did briefly attempt to start the cycle but then powered down again so I decided to plug in my GapIID to see what issue I had now expecting it to be the same.

To say that Gap was inconclusive is an understatement, according to it, I have every single component of my L322 in fault and I am not joking, it started with 40 ABS module faults, every part of the HVAC, transfer case, Instrument cluster, you name it! I cannot stress enough how bad it is according to GAP. I can clear them all and every single one comes straight back and they are all dated 13/5/2023. I gave up on that, I'll charge the battery as it only does short runs currently and revisit that issue another time so lets park that there for a moment.

Back to the FBH, Can anyone recommend a company that can test it for me or is anyone local is to Maidstone that I can bring it to for a look? I found Robinsonlabs website and videos, but I've emailed them and they haven't responded, they also don't have a phone number so I'm a bit sceptical about paying £70 and posting the circuit board in case they are no longer trading.

If it's the glow plug transistor at fault, I'd fairly happily replace it myself but I'm not good enough with electronics to know that I am testing it correctly and I don't have the diagnostic capabilities for this board so it would be guess work and that's not much good to me. Usually the transistor would have damage on it to see when they burn out and as you can see in this pic, mine looks to be in perfect health (I accept that looking like it and doing it are two very different things).

Click to expand...

Which component do you think is the glow plug transistor? If you think it's the one top left of the photo with the metal tab, I think you are wrong, hard to read the part number but I think that is a 5 volt regulator IC that provides the voltage for the micro processor chip. There are 2 transistors bottom left, one is a BTS132, the other unmarked. As the BTS132 can pass 24 amps, I suspect that is the glow plug transistor or possibly it's the unmarked one.

Datatek said:

Which component do you think is the glow plug transistor? If you think it's the one top left of the photo with the metal tab, I think you are wrong, hard to read the part number but I think that is a 5 volt regulator IC that provides the voltage for the micro processor chip. There are 2 transistors bottom left, one is a BTS132, the other unmarked. As the BTS132 can pass 24 amps, I suspect that is the glow plug transistor or possibly it's the unmarked one.

Click to expand...

The bottom left two are for the fan and pump but another search has revealed that one at the top left of the board as causing this issue. It may not directly the control the glow plug but if as you suggest it is for the microprocessor it could cause the error as in not being able to activate the one for the glow plug. This is where I need someone who can test it fully and repair it if it's at fault as I'm now just guessing.

Iv got the software and connection kit I built to run these off my laptop on my bench when I was going to retro fit a fbh to my m62 v8.

Robinson labs went defunct ages ago so stay away.

As it tried to start 1st time I think the board is fine but has locked out your gap tool should reset it and do a forced start if its the sames as the D3. The fbh lockout after so many false starts. Until its been cleared it won't run.

Let me have a look to see if iv still got everything in a box somewhere.

biketeacherdave said:

Iv got the software and connection kit I built to run these off my laptop on my bench when I was going to retro fit a fbh to my m62 v8.

Robinson labs went defunct ages ago so stay away.

As it tried to start 1st time I think the board is fine but has locked out your gap tool should reset it and do a forced start if its the sames as the D3. The fbh lockout after so many false starts. Until its been cleared it won't run.

Let me have a look to see if iv still got everything in a box somewhere.

Click to expand...

Top man, thanks!

There is a lot of info that suggests you need to pull fuse 59 (?) but when I checked, I don't have that anyway and as my car is a 2010 model it has the tele start pre-wired so there's every chance that LR moved some wiring around. As for my GapIID, I have no idea what's going on there but it fils to run the fuel priming or operation test which could of course be down to the lockout anyway.

You must remember they don't fire up below 5 or 6 degrees anyway which is why you either do a lockout reset with your gap tool then prime it check the pump is working its near the rear under the chassis you should hear a click click click as it pulses if its not priming chances are the pump is faulty....common issue.
Check the pump and report back it will take me a while to find all my kit as it's packed away.

Blob said:

The bottom left two are for the fan and pump but another search has revealed that one at the top left of the board as causing this issue. It may not directly the control the glow plug but if as you suggest it is for the microprocessor it could cause the error as in not being able to activate the one for the glow plug. This is where I need someone who can test it fully and repair it if it's at fault as I'm now just guessing.

Click to expand...

If you let me have the numbers off the one at the top, I can tell you what it is.

biketeacherdave said:

You must remember they don't fire up below 5 or 6 degrees anyway which is why you either do a lockout reset with your gap tool then prime it check the pump is working its near the rear under the chassis you should hear a click click click as it pulses if its not priming chances are the pump is faulty....common issue.
Check the pump and report back it will take me a while to find all my kit as it's packed away.

Click to expand...

If I'm honest, I haven't heard it, the coolant pump and fan runs up as part of the startup sequence but of course until there is fuel, we won't get a glow plug. I'll have to have a look underneath for the pump. I might just replace that anyway as it is likely seized up, I have no idea how long this thing has been inoperable.

Got the car on charge now as it dropped to 11.7v and that ain't enough for these things to work properly that's for sure. I'll test it a bit more tomorrow time permitting and see what happens.

Any recommendations on where to get a replacement pump?

You can test the pump by pulsing it with 12v and as you've got the fuel pipe disconnected you should see it coming out.
I'll see if I can dig out the pin connections for the plug.

I bought a test kit from these guys about 4 years ago https://fnltd.co.uk/shop/
You need the Webasto wtt software but I can't remember where I got that from but it looks like you can just download that.
Oh and a psu for bench testing. Obviously you can't fire it up without fuel but you can activate the pumps and the glow plug, and various other tests.

I've ordered a fuel pump for it, had a quick look under the car earlier but I couldn't see it, is it above the tank cover or accessible from under the seat (doubtful the seat) but if anyone knows please share.

Hi, my FL1 FBH (thermo top z) sometimes won't fire after three attempts & then 'locks out' so you won't hear the dosing pump anyway in the 'lock out' state. In this case with the ign. on pos ll I pull the fuse (under bonnet fuse box) to reset it it then fires with a cloud of smoke . The FL1 also only works below four degrees.

Blob said:

I've ordered a fuel pump for it, had a quick look under the car earlier but I couldn't see it, is it above the tank cover or accessible from under the seat (doubtful the seat) but if anyone knows please share.

Click to expand...

The FBH fuel pump is installed at the right-hand (RH) rear of the fuel tank, in a rubber mounting attached to the rear subframe

Pulling fuse 59 for a few seconds will reset the FBH.

I just followed this built my own lead, downloaded the software and used a spare battery and jump leads to run it from while on the bench

biketeacherdave said:

I just followed this built my own lead, downloaded the software and used a spare battery and jump leads to run it from while on the bench

Fuel Burning Heater - DISCO3.CO.UK Knowledge Base

disco3.co.uk

Click to expand...

D3 and L322 FBH are different. L322 is WBUS controlled.

backinblack said:

Pulling fuse 59 for a few seconds will reset the FBH.

Click to expand...

It's not fuse 59 on the facelift car, there's nothing in it and shows as not used on the diagram. Found quite a lot of people saying the same thing on the 2010> too. On FullfatRR there is a post saying it's in the under bonnet fusebox and saying it's Fuse E8. I didn't know there was a fusebox under the bonnet and I can't find any pics on it online either, just the ones in the glovebox and boot. This is a bit odd.

It's been out of the car for a few days now anyway so I assume it has reset. Until I can get fuel up there I'm not going to win whatever happens. If I try to run the priming function with Gap, it fails but I suspect that the dosing pump isn't separately controllable without the heater motherboard in place as it's on the bench but it didn't work beforehand either so I'm highly suspicious of the pump. Not only that, the heater itself was so clean inside that it doesn't look like it's done a huge amount of work and the car has 165k on the clock now so it may not have worked for years, hopefully just due to a failed fuel pump. The new one is expected by 10pm today so I'll hopefully get it fitted tomorrow and then we can move on from there. I will attempt to prime it with a syringe first as these things are really sensitive to lubrication and it will prove that it can draw from the tank with no other impedance. Bit at a time and all that.

I did jump the pins from the Telestart module and it kicked the fan and coolant pump on the other day when I refitted to test but then it turned off probably from lack of fuel pump etc. and wouldn't try again so I suspect it locked out again based on that. Obviously using the Telestart is only any good if the thing works, it's not a diagnostic device but I think it gave me a hint.

If you mean you are going to use a syringe to suck fuel from the FBH end then it won't work as the pump is a pulse type so you can't draw through it.
Yes the circuit board will need to be in place to automatically prime the pump but you can still apply 12v to the plug assuming it's the same as earlier models. The part number on your pcb is for Thermo top c so assume it is.
I got fuse 59 from the 2007-2010 manual.
If it's not been use for a long time it could take a few attempts for it to start up.

Found reference to fuse 19 on another forum.