I'm working on a 2001 A4 TDi and the blower is intermittant now it works less than it works. I've tried a different motor off ebay but this has the same fault?
Turn on climate control to auto and plug the unit in and it works for a few seconds then stops. If you remove and plug it in again straight away it may work again but for less time. This is the same on both motors. If you leave the unit installed as it should be it will not work after the first install.
I've checked power and earth and both are good. Also with a scope I've got data going to the blower on the Brown/black wire which changes when you change the fan speed, but on the yellow wire which I think is the motor return, when the fan is running for its short period you have data. This waveform is slightly distorted with a slopping front egde, and as soon as the motor stops you lose this data.
This is a later motor with a 8E2 prefix part number so no brushes to replace.
I've noticed quite a few people having intermittant A/C which comes and goes,
PLease can someone confirm that the fault is the motor itself or should I look else where.
Thanks

Ah, you have a TDi? No fair!

Sounds more like a bad resistor or possibly even the HVAC control unit itself. Usually when a fan motor goes bad, it just doesn't work. Diagnosis for the fan is to apply 12V ans see if it runs. If it does, look elsewhere.

Another possibility is that the HVAC control unit needs to be adapted via a VAGcom.

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01 A4 1.8T Quattro Sport
Eibach, Hotchkis, Upsolute, Borla

Courtesy of Mattzcrazy found in another thread:

http://www.audiworld.com/tech/int5.shtml

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01 A4 1.8T Quattro Sport
Eibach, Hotchkis, Upsolute, Borla

Thanks for your help.
I tried the On Board Diag. but this car has the Dual Climate Control and this diagnostic doesn't seem to work.
I managed to get hold of a wiring diagram for the heater system and on this model it doesn't appear to have the resistor all the control is built into the base of the motor. It appears to have no brushes and is controlled as a stepper motor.
This motor is controlled by changing the mark space ratio on the Brown/Black wire and to just apply 12v across the motor will not work. I think they may have put the new design for the B6 model into this as one of the last B5 models.
Pls help I may post tihs onto the B6 section as well?
Thanks again