Check temperature flap or servo motor - Audi Coupe

Hello,
Today, I briefly worked on a late 90s coupe where the temperature control system isn't functioning correctly. Specifically, the car is heating up regardless of the temperature setting. Out of desperation, since Audi claimed that a diagnosis and actuator test were not possible, I swapped the control unit with one from an identical vehicle, as this was supposedly a known issue.

No change!

'Definitely, after being exposed, the temperature control flap doesn't move. How can I check the control signal? Unfortunately, I have the somewhat uninformative manual, but not yet a wiring diagram.' Has anyone else experienced similar problems and can offer assistance?

Thank you, Tom.

Hi,
If it's a Klima system with a dual-display, it should definitely have a fault memory and a self-diagnostic function.
The climate control actuators are a recurring problem across all Audi model lines. The issue is that carbon dust, which forms on the commutator due to wear, eventually causes short circuits. This prevents the current from flowing through the motor windings, instead diverting it through the commutator itself. A solution can be either a completely new servo motor or disassembly, cleaning, and possibly replacement of the carbon brushes (which are compatible with those used in Märklin model train locomotives).
You can find the instructions on how to switch the climate control system into diagnostic mode, as well as the meaning of each channel, at http://www.meckisforum.de. If I remember correctly, it should also be possible to control the individual motors directly.

Best regards from Berlin.

Olli.

olli wrote:

If I remember correctly, it is also possible to specifically target the individual motors.

Yes, that's correct. The temperature control valve can be manually adjusted using the "+" and "-" buttons of the fan control system in channel 10 (setpoint temperature control valve).

THANK YOU.

Following update: After discussion, I was able to obtain a self-diagnosis and a functional test from the technician. Result: The pressure relief valve and temperature control valve are occasionally malfunctioning.

I opened the engines and now they're working again.

Best, Tom (but still installing new ones).

myfisch wrote:

Pressure relief valve

Did you manage to do it without removing the dashboard and the entire ventilation system?