# Aux heater metering pump



## robbie-rocket-pants (Mar 25, 2012)

Hi all,

I did a VCDS scan on my 2011 3.0TDi and it showed fault codes for the Aux Heater of "No flame" and eventually "Heater locked out". This fault was logged not long after the car was new, so the Aux Heater must have hardly ever worked.
I used VCDS to unlock the heater and clear the the fault codes but although it tries to start, it will not fire up, again coming up with the fault code of "No Flame". I also noticed that if I put my hand under the aux heater exhaust when it was trying to start there was no smell of unburnt diesel.

So I did a VCDS Output Test - all seems well but when testing the Dosing/Metering Pump (V54) I was expecting to hear a light thumping sound every few seconds (as my GP2 did when starting the aux heater). 

Do any experts out there agree that I should hear the sound of the pump when testing, and if it is the pump that is faulty please could you tell me whereabouts on the car it is ?

Cheers, Rob


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## n968412L (Apr 23, 2009)

Hi Rob - can't add much to what you already know. I don't specifically know that you'd hear the pump when testing as I've never done it. However as on your GP2, my GP0 and GP1 both have audible pumping. It sounds as though the pump is at the left rear of the car... I've got somewhere the self study guides... I'm not sure they'll help you much, but they might. however I'm aware from home at the moment. If no one else can post them up or send them, I'll have a look when I get home at the weekend.

Mike


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## snapdragon (Aug 8, 2006)

I'm no expert either but would expect to hear a the thumping of which you speak and a sort of high-speed fan noise..


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## robbie-rocket-pants (Mar 25, 2012)

Thanks very much guys. I'll go for a look under the rear left of the car.


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## robbie-rocket-pants (Mar 25, 2012)

I've been for an extended rummage under the car. The Webasto Dosing/Metering fuel pump is fitted above the rear left driveshaft area. The VW repair manual (which I found on line) says that the rear subframe has to be dropped to get to it. I thought I might just be able to get to it without doing that and I nearly succeeded, being scuppered at the last hurdle by the very short fuel inlet pipe which didn't quite allow me to pull the pump out enough to change it, so I'll have to pay someone with a ramp to do it. 

I did however manage to pull the outlet pipe off and then tested the pump with VCDS - as suspected almost no fuel came out of it so its either the pump or a blockage in the inlet pipe.

As an aside, when I was researching the aux heater (Webasto Therno Top C) I came across this procedure which I think may be handy if your heater locks out and you don't have VCDS to hand:

*6.3 Heater Lockout Reset Procedure

The TTC is designed with a lockout safety feature built in to the control unit. After 3 consecutive
unsuccessful startup attempts, the heater will lock itself out from any further start attempts. The
heater may also enter the lockout mode after experiencing an overheat condition.

The following procedure will clear the lockout mode and reset the heater for normal operation:

1. Remove fuse F1 (15 Amp), refer to wiring diagram figure 411 for identification.
Wait 10 seconds before reinserting. This is done to prepare the control unit for resetting.
2. Wait a further 10 seconds after reinserting fuse F1. Now turn the heater on using the On/Off
switch or the fiinstan onf button of the optional timer.
3. Wait 10 seconds after turning the heater on and remove fuse F1 again.
4. Wait a further 30 seconds and then turn the heater off at the switch or optional timer.
5. Reinsert fuse F1 after waiting 3 to 10 seconds of shutting off the heater.
6. Wait a further 10 seconds and turn the heater back on again.
The lockout mode should now be canceled and the heater operating normally*

Obtained from www.techwebasto.com/redirect/heater_main/907512.pdf

I believe the fuse it mentions would be fuse 16 under the steering wheel


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## robbie-rocket-pants (Mar 25, 2012)

I persevered and, after much skinning of my knuckles, managed to get old the metering pump out without dropping the subframe. It was incredibly fiddly. 

I extended the inlet hose by using a straight connector and about 20cm of 5mm fuel hose then fitted a new pump. I used the VCDS output test to run the pump a few times and get fuel to the aux heater. 

Hey presto ! Fixed. I'll be glad of my work when the Winter arrives 

Here's a picture of the old pump. I decided to teach it a lesson and cut it up - it is just a solenoid with a piston in it.


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## n968412L (Apr 23, 2009)

Hi Rob - thanks for the info. Good to know that these can fail - although I've never heard of it before.

The armature seems to have some burning in it - or is that damage from cutting it open?

Regards

Mike


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## robbie-rocket-pants (Mar 25, 2012)

Hi Mike, 
the burning is from cutting it open. I'm not sure why it failed but I think the piston must have got stuck judging by the very weak pulsing I felt while testing it with VCDS.
Cheers, Rob


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