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DISCO4.COM > Webasto Fuel Burning Heater

FBH not working.

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ianrichardson

Member Since: 31 Aug 2010
Location: Cardiff and Mid France!
Posts: 313

2006 Discovery 3 TDV6 HSE Auto Santorini Black

FBH not working.

Hi all,

My IID Tool is giving me this fault

Auxilary Heater

B1D25-15 (2E) Dosing pump circuit - General electrical failure - circuit short to battery or open

Clear the DTCs and do another test gives

B1D25-15 (2F) Dosing pump circuit - General electrical failure - circuit short to battery or open

(2E to 2F!)

I've tried priming the pump and that shows 'success'.

When I try to force it to operate with my IID Tool I get 'Operation Failed E 7'

Any ideas where I should start to find out where the problem lies.

Ian

11th Jan 2018 5:14 pm

Pete K

Member Since: 15 Jan 2016
Location: GL
Posts: 10676

2005 Discovery 3 TDV6 HSE Auto Rimini Red

well there is a small pump for the FBH just infront of the fuel tank.

I don't know if this is the "Dosing pump" though

Wires leave the FBH and drive that pump and should be obvious.

Maybe disconnect the wires and continuity check, and make sure the wires aren't chaffing against the chassis, which seams to be all too common on these cars

11th Jan 2018 6:07 pm

ianrichardson

Member Since: 31 Aug 2010
Location: Cardiff and Mid France!
Posts: 313

Hi Pete

I've pulled up the circuit diagram for the FBH.

Click image to enlarge

I can see that the pump is fed from pin 5 of the 7 pin socket on the FBH, so my first task is to check voltages there and also see if there is a reasonable resistance that you would associate with a motor. Then see if I can make the pump work independently of the FBH by applying 12v on that wire.
I'm making an assumption that that is the 'dosing' pump!

Any thoughts?

Ian

12th Jan 2018 9:32 am

Pete K

Member Since: 15 Jan 2016
Location: GL
Posts: 10676

can't see the diagram ATM
But yes.
just ensure you aren't confusing the pin numbers for the water pump and fuel pump.

12th Jan 2018 12:09 pm

Martin
Site Admin and Owner

Member Since: 06 Nov 2004
Location: Hook Norton
Posts: 18561

2006 Discovery 3 TDV6 SE Manual Buckingham Blue

Pin 5 is the fuel pump but it is a solenoid dosing pump not a motor. Apply 12V in pulses and listen for the pump ticking. It doesn't whirr with constant voltage unlike a typical car fuel pump. 06 D3 SE / 15 LR D90 XS SW / 88 LR 90 Td5 / 68 BMW 2000 ti
Any issues with the site let me know!

12th Jan 2018 7:26 pm

ianrichardson

Member Since: 31 Aug 2010
Location: Cardiff and Mid France!
Posts: 313

Hi Pete and Martin

Thank you both.

Martin are you saying that it works like a SU pump of old but rather than the pump having the solenoid the FBH sends pulses to actuate it?

If this is the case, with the IID Tool I can 'prime' the system and so 'should' hear the 'pump' working?
I could try and see if the FBH is sending pulses along that wire I suppose.

Ian

13th Jan 2018 9:29 am

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