Where does the FBH take it's coolant temp reading from?
Morning,
I'm trying to get to the bottom of an intermittent FBH start that i've started to suffer with.
The FBH was working on spec until a recent visit to the dealers. Now it seems to start ad hoc.
I can start it both with the Webasto software when it runs as it should with no fault & no faults in the memory. I can also start it with the IID Tool with no issues. But left to it's own devices it appears to start randomly when I'd expect it to be running.
So the car has sat overnight, measured temp on the ambient temp sensor is less than 5Deg, full tank of fuel. Engine cold. Start the vehicle, leave it to runs for 5 minute or so, no sign of the FBH even attempting to start. On other occasions it will fire & run quite happily.
A couple of scenarios I can think of.
1. When it was in the dealer last they replaced the EGR cooling hose as it rubbed on the auxiliary belt following a EGR valve replacement. During this process has something been dislodged & not replaced correctly? Hence asking where the coolant temp it read from.
2.The glowplugs are kaput on my D3 & it takes some time to fire up on the first start of the morning. Could this additonal draw from cranking be pulling the current down enough to prevent the ATCM from calling the FBH to start? The voltage at cold according to the IID tool is 11.9V, which is in spec according to the LR manuals. The battery was replaced last year with an Exide EA1000 due to HDC errors on start up.
I can't see anything obvious to give reason for it not to start. If I can start it manually through the IID tool then the wiring in the vehicle should be good? So it must be a parameter that isn't being met to call it into action.
It has power
It has fuel
I presume as the instrument panel reads 5deg or below that the sensor in the front bumper is connected & working.
This just leaves me wondering about the coolant temperature sensor, or any other sensor in the area of the FBH EGR, battery box that might have been disturbed & only working intermittently.
Any thoughts from my learned friends?
Cheers
NickMY16 D4 Landmark SDV6 (The Ice Maiden)
Uncle Ray's spare wheel protector
MY08 D3 HSE Stornoway (Miss Moneypit) The money tree withered......
11th Jan 2018 10:56 am
Mole734
Member Since: 12 Aug 2016
Location: Derbyshire
Posts: 162
There is a water temperature sensor in the body of the heat exchanger, its viewable in the IID tool under live values/aux heater/coolant temperature note that this is a different sensor to live values/engine/coolant temperature (the latter one goes offline when the ignition is off the former does not)
Sensor mentioned in section 2.3 of the FBH manual here
So that should eradicate the coolant sensor from the equation if it forms part of the FBH & the Webasto software shows everything working correctly.
When the missus is back with the D3 later i'll check the sensor in the IID live values to see what it's reporting for good measure.
I have got the original FBH here which i can rob for spares if i need to get to that point but i think it's a outside variable that causing the inconsistent starting rather than the FBH unit itself.
I'm leaning towards the lack of current on first start up. I think i might try starting it when the weather temp is in spec, run it for a short period, then let the car go to sleep & start it again. This time the car should still be cold enough to require the FBH but warm enough to start easily given the glowplug issue & demand less current due to a reduced crank load.
Keep you posted......
NickMY16 D4 Landmark SDV6 (The Ice Maiden)
Uncle Ray's spare wheel protector
MY08 D3 HSE Stornoway (Miss Moneypit) The money tree withered......
11th Jan 2018 12:36 pm
zinke
Member Since: 22 Feb 2014
Location: Scunthorpe
Posts: 584
Not had time to read though this fully so might not be relevant.
My fbh is the same as yours, doesn’t run when expected sometimes but always fires on the wtt software or using the iid. Left to its own devices some mornings it fires some it doesn’t.
So gave it a service and checked glow plug etc but still started randomly.
So had a word with Robbie a few days ago and he suggested checking the fuel pump. As far as I could work out it should supply 40ml of fuel in 180 seconds. After runnin the test 4 times I got 28-29ml each time which isn’t enough as far as I can work out, it’s supposed to be 40.
So at the moment I’m in the process of trying to find a good used pump to swap out with mine to see if this helps resolve the problem.
If anybody has a spare pump kicking about please let me know!!!
Pete.IID, webasto software and workshop facility's available.
11th Jan 2018 2:03 pm
zinke
Member Since: 22 Feb 2014
Location: Scunthorpe
Posts: 584
Also to add, I thought about low voltage causing the issues but have ruled that out in my case. I’ve also noticed that if you get out after you start the fbh always try’s to fire when it should, it just doesn’t run. Looking on the iid there is no fault code but using the wtt software or altox it shows “02h” or “02” fault codes.
Pete.IID, webasto software and workshop facility's available.
I guess if they removed the FBH to get to the Egr Coolant hose the maybe the fueline could have an airlock. Perhaps worth purging it in my case.
I forget at what stage the FBH primes but I don't think it's even starting an ignition sequence
Cheers NickMY16 D4 Landmark SDV6 (The Ice Maiden)
Uncle Ray's spare wheel protector
MY08 D3 HSE Stornoway (Miss Moneypit) The money tree withered......
11th Jan 2018 2:09 pm
Mole734
Member Since: 12 Aug 2016
Location: Derbyshire
Posts: 162
Just a thought, you can disable the FBH from starting by turning off the climate control, that way you can get the engine running before turning the climate/FBH back on. Should then provide full voltage/current for FBH start...
11th Jan 2018 2:11 pm
zinke
Member Since: 22 Feb 2014
Location: Scunthorpe
Posts: 584
If you have the cable and wtt software then it’s a quick job to check the output of the pump.
Pete.IID, webasto software and workshop facility's available.
11th Jan 2018 2:23 pm
M3DPO
Member Since: 22 Sep 2010
Location: Notts.
Posts: 8244
Don't forget the climate control has to be switched on if only in Eco mode for the FBH to run.It can when others can't,
It will when others won't,
It goes where others don't.
So as an update I waited this evening until the outside temp has dropped & the coolant temp had fallen to below 75deg.
Started the D3 & a few moments later the FBH fired
I conclude that the only difference is that the car was still warm from the drive home earlier in the day & therefore started easily with less current draw hence the FBH fired.
Compared to the morning when the car needs to crank harder resulting in reduced current, then this preventing the FBH from starting.
So i'll try starting in the morning with the Climate off, then turn the climate on a minute or so later & see if that results in a FBH fire.
Never a dull moment with D3 ownership eh?
Nick
MY16 D4 Landmark SDV6 (The Ice Maiden)
Uncle Ray's spare wheel protector
MY08 D3 HSE Stornoway (Miss Moneypit) The money tree withered......
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