No Heater Blower

[carl81]

Hello,

I have a problem that I have no heater blower on my Audi A6 C6 3.0tdi 2006. The fault from VCDS on the HVAC unit is:

1 Fault Found:
02071 - Local Databus
012 - Electrical Fault in Circuit

Fuses are fine. Now an internet search seems to reveal that unplugging the G395 Air Con Pressure switch allows the fan at least to start working. Due to a short of some kind interfering with the comms / bus. I have unplugged mine but still no blower. Could the actual connector be causing the short for instance?

Any idea what to try next? A new blower unit is the obvious choice but the VCDS error concerns me that this wont fix it. The blower just has a positive and negative terminal so I'm not convinced this will help with the databus fault?

[Crasher]

What is the VIN?

[carl81]

What is the VIN?

WAUZZZ4F86N162208


Thanks.

[Crasher]

Check fuse 41 in the right dash side fuse board has power across it, if it does my initial suspicion would be the F126 blower controller 4F0 820 521 A, the fan itself is easy to test

[carl81]

Thanks. My thoughts too.Fuse is all good. Already ordered the heater controller. 😁

[carl81]

Replaced the heater controller / resistor and got the same problem. Also put 12v on the fan. It worked fine.

Now lost. Any thoughts?

[Crasher]

You have checked for power on the red/blue wire where it changes to red/black at the 3 pin plug?

[carl81]

You have checked for power on the red/blue wire where it changes to red/black at the 3 pin plug?

So the red and black has 12v. The red and blue has nothing.
plug.jpg

[carl81]

There is 0.5v on the yellow.

[Crasher]

It is black/yellow on the diagram, that is the control head signal line