# Help: Auxiliary heater does not operate correctly.



## Gabs08PHTN (Jan 6, 2011)

Dear all,
Now that the weather is cold enough to start using the auxiliary heater to preheat my Phaeton in the mornings, the heater has decided not to work correctly.
If I program it, it starts as usual, but after a few minutes the burner stops and goes into control pause (I have checked it with VCDS and the reason is that it reaches 89ºC). After a while it comes on, but stops shortly afterwards and keeps on cycling that way. In addition to that, the air coming out from the defroster nozzles is barely warm. Alternatively I press the Aux. Heating button it behaves the same way. So it does with the engine running.
I have tried to diagnose what is wrong with VCDS but it does not show any faults at all. I have also run the output tests and all seems fine. However, when I activate the recirculation pump V55, it does not make any sound at all (I seem to remember that it made a whinning/humming noise), despite VCDS shows no fault. 
I believe that either the pump is faulty, therefore the flow rate of coolant inside the heater is too low to cool it down, or the temperature sensor is faulty and measures a higher coolant temperature than it should.
So, could someone please, activate V55 pump with vcds and confirm what sort of sound it makes and also compare the auxiliary heater temperature sensor reading with those of the engine temperature sensor and the HVAC heater core temperature sensor? I would really appreciate it. 
Many thanks in advance.

Gabriel


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## Gabs08PHTN (Jan 6, 2011)

A short update:
Removed the auxiliary heater fuse. 
Plugged the multimeter probes to both fuse holder connectors.
Measured the current while enabling the fan, glowplug, fuel pump and water pump with VCDS. All, but the water pump show current going through it.
So it seems that the either the pump is shot or the control electronics inside the heater are faulty. 
Any ideas?

Gabriel


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## Gabs08PHTN (Jan 6, 2011)

Next Tuesday I have an appointment at the local VW service to diagnose what is wrong with the heater.
I have also spoken with the Webasto service in Madrid. They told me that the control unit software does not allow them to fully scan the unit. They can only read some fault codes, but provided that VW finds out what is wrong with it, they can fix it. Just in case it was necessary I have already purchased some 12kohm thermistors.
As it is very likely that the heater has to come out, I have also purchased a set of Osram night breaker D1S lamps in order to have the original ones replaced as one of them was flikering at times.
Nevertheless if somebody in the forum could please spare some time over the weekend testing the heater as indicated in my first post would be great.

Gabriel


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## Tedo (Apr 20, 2015)

In my case, the Webasto water pump was faulty. You can hear the pump when it's running.

You can buy replacement Webasto water pump directly form Webasto. Down side is, that generic Webasto pump have different positions of inlet and outlet pipes on the top of the pump. But not to worry, the top part of the pump can be exchanged with the current one that you have. And also the new pump have different connector and shorter cable...so a bit of a DIY is needed 

When filling up the cooling system, make sure that no air is trapped. If an air bubble is inside the water pump it won't work at all.


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## Gabs08PHTN (Jan 6, 2011)

Thanks for the info Tedo.
Much appreciated. :thumbup::thumbup::thumbup:

Gabriel.


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## Gabs08PHTN (Jan 6, 2011)

Well, the Phaeton is still at the VW dealer where the heater was disassembled and checked. It turned out that the coolant pump was faulty as anticipated.
I took the heater to the local Webasto dealer to have it serviced. I mentioned to them that when the engine is at operating temperature the NTC sensor reading is about 20ºC higher than the coolant temperature sensor of the engine. According to them, all was fine other than some soot, which was removed, at the combustion chamber. They also concluded that the pump was faulty. 
Despite Webasto said that the NTC sensor was fine I am still dubious about it. I have already purchased a set of 12kohm thermistors so I am ready to replace it if needed. What do you reckon guys? If you could provide some temperature readings of the heater temperature sensor and the engine coolant sensor for comparison it would be great.

Gabriel


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

Hi Gabriel,
I'm not sure which measuring blocks to look at, but is this of any help ? My car is cold with the heater off.









Robbie


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## Gabs08PHTN (Jan 6, 2011)

Thanks Robbie,
Could you also provide the engine temperature reading (when cold)? I mean via the engine measuring blocks.
And, if you do not mind me asking, I would very much appreciate if you could give me the heater and engine temperature readings with the engine at operating temperature. 
I am sorry to cause you so much hassle, but so far you are the only one who is giving me a hand with this issue.

Gabriel


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

No problem Gabriel.
The cold engine temp is 2.7deg C.
I'll have to wait a few days till I can get the engine warm as it's off the road for a bit.


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

Hi Gabriel,
here is the warm engine data:

Engine temp: 82.8 deg C
Aux heater group 001: 65 deg C
Aux heater group 006: 7 deg C
Outside air temp: 6.5 deg C


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## Gabs08PHTN (Jan 6, 2011)

Thanks a lot!!!
That is very odd.
Mine measured 20C above engine temperature and yours 20C below.
There must be something going on with the temperature sensor of the webasto heater as it ages I guess.

Gabriel


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## Gabs08PHTN (Jan 6, 2011)

Hi all,
Just to finish off my auxiliary heater malfunctioning event:
As I was not very satisfied with the interest that the local Webasto technician payed to my requests, I decided to inspect the job he had carried out. To my dismay, not only he had not replaced any gaskets at all, but he had broken and reinstalled the conmbustion chamber gasket that isolates the combustion chamber from the blower side of the heater :banghead::banghead::banghead:.
I was lucky that my local VW dealer had a set of gaskets available, which I purchased and fit to the heater. 
Also, due to the fact that the coolant temperature sensor readings were somehow odd, I decided to bit the bullet and replace it too. The hardest part of the job was to drill out the bottom fasteners that secured the control unit cover as they snapped and were very badly corroded.
The set of 12kohm NTCs that I had bought were not flat as the OEM part, but round. For that reason I had to drill a small receptacle at the upstand where it sits in order to secure it. See pictures below.



















After restraining the NTC with the spring plate, I reinstalled the cover with the original seals, fastened it with new bolts and sealed it with heat resistant aluminium tape.











Subsequently, I took the overhauled heater to my local VW dealer where a new pump was attached to it and the whole pack was reinstalled onto my Phaeton, together with a wire plugged to pin #1 of the auxiliary heater six pin connector.
In addition to that, I took the oportunity to have both xenon lamps replaced with new Osram Xenarc Night Breakers (as the righ OEM lamp was flickering intermitently) and to have the intercoolers and radiators pressure cleaned.
Later on, at home, I installed a Telestart T91 remote control. I placed the control unit on top of the steering fluid reservoir and, as it is a temporary installation I am plannning to install in the rear parcel shelf, current was fed from the TV22 junction.
I have been using the auxiliary heater regularly after it was fixed and now the interior of the Phaeton seems way warmer than before, so it is quite likely that despite there was no indication that the pump was faulty, it must have been operating badly for a while. 
Nevertheless the coolant temperature reading of the heater is still higher than that of the engine temperature sensor. My guess is that as the coolant pick up point of the heater is located at the hot side of the coolant circuit, next to the radiator, the coolant temperature there is higher than at the location of the engine temperature sensor.

Merry Christmas everyone :biggrinsanta:

Gabriel.


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