yoni_d

Hi guys,

I have 928 1980 Euro model.
Today I noticed that when I start my car, the AC starts to work even though the HVAC (lower) lever is at the most left position (off).
I have located the wire that should carry the signal from the HVAC lever and it seems that when the car is on, the voltage on this wire is about 8 volts (not 0 as it should?) and this makes the AC relay to kick in. When I move the lever one step to the right (ECO) the voltage is 12V so the AC is also (still) on although it shouldn't.
When the lever is moved to the central position (automatic) the wire still carries 12V and the AC is on. This is actually the first position in which the AC should start working...

Have you seen such phenomenon?
Do you have any idea how this can happen or how the lever should work?

Thanks for your help.

dr bob

There are a couple isolation diodes for the relay in the HVAC control head that usually keep this from happening. You can test them in circuit with a DMM. They are low-load low-voltage duty, OK to replace them with common 1N4001 silicon diodes on the circuit board. Watch for correct polarity when you replace.

yoni_d

Thanks a lot for the tip!
I will try this in the weekend...hope this is indeed the issue.