Heikowirth

Hi all,

I'm new on Rennlist - Heiko, 928S MY81, from Germany :-) Thanks for this forum :-)

I have an issue with my HVAC and evtl. a potential root cause found...would be great to have your opinions on this:

Issue:
- Solenoid valves HVAC not working
- Ground wire of solenoid valve panel goes to Pin 9 HVAC controller
- Separate ground wire attached makes them work incl. Flaps

After some research hours in the internet I have the following theorie to the issue - of course to be proven on the car Porsche designed a fail safe mode in the HVAC system - in case of a defect of the HVAC unit, the AC relay (original the yellow one on the PCB of the HVAC coontroller, which is not very robust) will not be engaged to turn on the compressor (AC clutch). The ground line (Pin 9 HVAC Controller) of solenoid valves is also switched by this relay - or not, in case of an issue. In consequence e.g. the center flaps are not engaged too (means closed) - this helps, not to blow cold air (cold engine) in the face of the driver (fail safe mode). So I need to check, whether the relay on the PCB is still in working condition...if not, this is the issue.

Opinions welcome...curious to read your comments

Cheers, Heiko

Heikowirth

News: I have changed the HVAC Controller relay yesterday, and ... the solenoids are working perfectly.

For all those driving MY81, if solenoids not working, it might be the relay (as in my case).

Cheers,

Heiko