Member Since: 25 Jan 2019
Location: hampshire
Posts: 29
FBH fixed with donor parts
Hi all - posting as a fix here - should anyone benefit from it.
Huge thanks to Robbie and Martin for your wisdom.
Car/FBH - 2011 3.0 HSE 125K road miles with Thermotop V FBH.
Symptoms:
November/December: Slow warm up, poor cabin heat, no evidence of fbh working
I suspected FBH problem and probably thermostat too.
[edit: cabin heat now good when engine up to temp - having topped up coolant and re-bled]
Diagnosis:
FBH not kicking in on cold (<2C) starts. No smoke, noise or heat from FBH unit.
Ran reader (autel) and found dosing pump issue - (and possibly wiring from reading other posts)
Made up diagnostic cables for Webasto software and plugged in. Same issue - pump.
Found dosing pump, noticed that it had been unplugged (either previous owner or LR(!) when they replaced the tank sender cabling?) - anyways, re connected the pump plug.
Ran Webasto diagnostic again. Pump problem gone. Won't start though (also get "NAK: access denied" error), but other functions working separately (glow, pumps, fan etc - and did the measuring trick for the dosing pump) - so i know that the software is chatting to the unit at least. (using either 2.16.1 or 2.14 versions of the software on com3/usb by the way)
Cleared faults for good measure to start with. (no change - still not working)
Dismantle/clean FBH
Extracted FBH for further examination - connecting the coolant loop and bagging/plugging other connectors in the meantime.
Dismantled FBH - remarkably clean and seals / gaskets in good nick - but diesely / moist. Probably due to overpriming and non ignition.
Made further dismantle (burner unit) - found cracks in the ceramic. (pics) - but the rest of it (glow plug, 'cup' etc) were in great nick.
From what I understand, these cracks in the ceramic means a whole new burner unit!
Seemed like a huge waste (for such a small failed part) - so challenge was finding supply options for a replacement ceramic burner part.
My thinking: Worst case will be new burner unit so nothing to lose in trying alternatives.
Solution - salvage sound ceramic from another unit.
Bought this from yeabay (from a 2007 RRS - but still a Themotop V) - (~£60) almost identical to mine.
I figured at least I'll have some further spares to hand that way too!
Dismantled RRS unit - overall in much worse state than mine - sooty and some corrosion; seals & gasket poor condition.
Ceramic burner part looks complete and very close to identical to mine (slightly different 'fin' design)- just a little chip near the glowplug hole - hopefully not a huge issue. But key point - no cracks through it.
VERY carefully extracted the ceramic and part of gasket - tweezers, surgeon's hands etc.
Reinstalled salvaged gasket and ceramic to my burner.
Cleaned up exchanger and all around, and rebuilt with new gasket and o-rings.
Reinstalled to D4 and bled coolant.
===============
Still didn't fire up.
Diagnostics:
Webasto software gives me STFL and occasionally error 81h and 22h (EOL checksum)
Checked separate functions (glow, pumps, dosing amount, fan, etc - all still ok)
Still unable to start the unit from webasto software ("NAK: access denied")
Researched around the 22h error and the supposed 800hour operating ceiling and reprogramming EEPROMs [see here] - but decided that's for another day as i had a spare board from the salvage RRS unit that was worth a try.
Extracted board from salvage unit:
4 screws and a gentle pry
Board looked in decent shape, so installed it carefully into the original unit already back on the disco (didn't need to take it all off / apart again because the board side has decent enough access in-situ - just take plugs and fuel line off and pop the cover).
====
Side note:
The RRS unit didn't have pre-heating on the fuel line/injector (on the top of the burner part) - the plug was blanked. I plugged mine in (as it has pre-heat) and all seems well (see below).
====
Gently tightened everything up again, reattached plugs and fuel line.
Reconnected webasto diagnostics (so i could see what was going on) and prayed.
SUCCESS!
- Comms established.
- Read and deleted errors (because they were left over from the previous RRS use).
- Started a burn (no NAK errors this time).
- Glow kicked in, fuel pumped, fan started, flame detected, glow stepped back down
- Lots of smoke - as burning off probably 5yrs of non use in the exhaust!
Let it run for 15-20mins until no smoke.
Stopped and cool-down.
Next day tried it again. (via webasto software as outside temp not low enough).
All good. a little startup / warmup smoke then clean burn.
Very very chuffed it's working!
Think i'm sorted now - just need a cold day to see if it's starting automatically.
Thanks again for the board's knowledge and wisdom. Hope this helps someone.
arb
PS> in my EEPROM research (see above), i came across the 'engineering version' of the webasto software with some added functionality - don't know if that's useful, but Martin (I guess) - let me know if allowed / appropriate / useful for the board to have.
2nd Feb 2021 12:14 pm
leroymusic00
Member Since: 12 Jan 2021
Location: Carlisle
Posts: 143
FBH
Hi there - I cannot seem to get into the Aux heater on my Autel unit. It lets me go into the Diagnostics and look at everything being turned OFF but in the service section, there is nothing there to guide me to the FBH. How did you get into that part of the menu?
5th Mar 2021 7:35 pm
Motolab
Member Since: 18 Oct 2019
Location: Sleen
Posts: 1820
Re: FBH fixed with donor parts
arb wrote:
, i came across the 'engineering version' of the webasto software with some added functionality - don't know if that's useful, but Martin (I guess) - let me know if allowed / appropriate / useful for the board to have.
I advice to NOT publish that version (here) , you can very very easy brick the ecu permanently..
I read here very often allready that people, play allready with the co2 adjustments possibility in the default version... which is absolute nonsens most of the time.... let alone the version who can adjust almost everything...
I guess if people think they need it and are up to the job, they can PM you, but again publish it, for everyone to see here on the forum.... not a smart idea.... besides that i doubt that version is legal to use and publish for freeBest regards
Harold
Always looking for Pre '55's & Pre war British Motorcycles! knowing or having one for sale? PM please. I visit the UK 6 times a year
Ps. I edit my texts quite often, english is not my native language, so I will edit My “typo’s” etc.
5th Mar 2021 8:51 pm
arb
Member Since: 25 Jan 2019
Location: hampshire
Posts: 29
Re: FBH
leroymusic00 wrote:
Hi there - I cannot seem to get into the Aux heater on my Autel unit. It lets me go into the Diagnostics and look at everything being turned OFF but in the service section, there is nothing there to guide me to the FBH. How did you get into that part of the menu?
Hi there - yep, the FBH doesn't feature on the Autel service menu (wish it did).
For me, it only seems to come up in the diagnostics side when there's a problem with it:
I had it come up twice - once when the dosing pump was disconnected, and another when i had a D3 FBH board in my D4 (they don't talk to eachother).
When it does come up on the Autel, it's in the AHCM (auxiliary heater control module) part of the diagnostics.
When there is a problem with the FBH, there are options on the Autel to 'dig' further - a diagnostic test burn, as well as priming, was offered to me. That didn't work for me because of the comms error between D4 and D3 board in the FBH (mentioned above).
But, net net, when FBH is working fine (which mine is now), I can't seem to get to those other testing functions. Tried a few times.
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