AC to max with lights turned on

[Porschelibrarian]

Excuse me if this is elsewhere butbI didn't see it.   

 

I am getting a dead battery once a week and the battery, alternator and cables check out ok.  I noticed that when I turn the headlights on the a/c will turn on compressor and fan to max and if I turn the fan down it will again climb right back up on its own.

 

 

Any help guys?

[JFP in PA]

Sounds like you either have a very large parasitic power drain, a dying battery, or your charging system is malfunctioning, or some combination of these issues.

 

Have the battery and the alternator load tested, many auto parts stores will do this for free.  If everything checks out OK, you need to perform a parasitic drain test, which has been written up here and elsewhere multiple times, to identify which electrical circuit is the issue.  As for the car's weird behavior, weak batteries and charging systems are well known for causing all sorts of strange behavior in these cars.

 

Good luck!

[Porschelibrarian]

Battery, alternator, and cables were tested and fine.   I'm checking if one of the local Porsche shops I assist have an extra working A/C control module to swap and check

[jpflip]

I saw many strange electrical and electronic behaviours cause by the ignition switch...Not too expensive and not to difficult to replace....

 

https://www.6speedonline.com/forums/996-turbo-gt2/396010-bad-ignition-switch-advice-w-correct-996tt-part-number-diy-2.html

[987_RDC]

Sounds like something weird with the CAN bus if not the ignition switch. Perhaps disconnect and reconnect that unit.

[Porschelibrarian]

I should have posted this earlier but the simplest thing to try first was to swap out the A/C control module and its worked fine since.   I borrowed one from a local shop and since that worked I bought what looked like a clean ( returnable ) unit on Ebay for $200 and its worked fine since.

[Silver_TT]

Thank you for following up and posting the solution.