Blower motor always on!
 

Recently the blower motor on my 96 A8 has started acting up and refuses to blow at any speed other than maximum while the ignition or engine is on, even when the AC control unit is set to off. At the moment I've worked around this by removing the fuse from the yellow row, column 5.

Now before all this I had no ambient temperature on the instrument panel display, but after pulling the fuse it now shows a constant -27C which told me the ambient temperature sensor was failing. The problem persisted after replacing the G17 ambient sensor behind the bumper. With the fuse back in place the car is as before (Blower motor always on, no ambient temperature on display).

The previous owner replaced the dashboard with the facelift version including the AC controller. The instrument cluster is still the preface version. Could there be a mismatch with the connection between the AC controller and the instrument cluster?

I got 3 error codes from the HVAC system:

01317 - Instrument Cluster (J285): No Communications
01273 - Fresh Air Blower (V2)
01314 - Engine Control Module: No Communications

If the temperature sensor has failed wouldnt that possibly make the fan stay on all the time trying to bring the temperature up to a level it doesn't need to achieve? have you tried just controlling the blower fan on manual controls or won't it respond at all?

01273 code and fan always on at full speed is most likely because blower controller/resistor pack is faulty.

Other 2 codes because FL AC unit uses CANBUS for communications with the rest of car but PF car does not have CANBUS and uses K-line + separate signal wires. So you would need to fit CAN gateway that will translate signals.

If by manual controls you mean the fan speed on the AC controller then these do not work. Also ironically the only way to get heating in the car seems to be without the fuse as hot air will seep in from the air vents when the engine heats up. With the AC on it seems to only blow slightly cool air, regardless of temperature settings.

I've ordered a regulator, I'll keep this thread updated with results when it arrives. As for the CANbus, any idea if there are any adapters available or would I have to make one myself? Tried googling for one but seemingly no hits. I guess the preface one isn't standardized or anything so I'm fearing the latter option..