vonhummel

First I will apologize for another CCU Thread. I have searched and have not found another thread with the same issue.
'93 C2. Everything works fine when car is first started and driven for about 15 min or so. All servos work and temp selector functions. After the "warm up" all functions other than the fans stop working.
I have cleaned the temp sensor. The ccu fan stops running after 15 seconds or so after turning engine off. Fuse in Fuse box replaced. Failed engine fan resistor and temp sensor were replaced. Oil cooler resistor test fine.
While driving and after the CCU stops functioning it will occasionally start working and the fresh air servo will change or the AC compressor will start cooling the air then stop again after a few minutes.
Seems to be temp/time related. Is there a relay that could be failing or something else that when it gets warm it looses contact?


Thank you for you help,
Brad

heliolps2

I had the same issue and did much the same things you did. Finally, I sent out to ECU Doctors, and no issues since. that was 2018. Great investment and ice-cold air.

heliolps2

I had the same issue and did much the same things you did. Finally, I sent out to ECU Doctors, and no issues since. that was 2018. Great investment and ice-cold air.
Helio

0luke1

Same here ECU Doctors +1. Great people.

systemsc

Tap on the control panel of the CCU, to determine if it has an intermittency, and check and use WD-40 on the two rear connectors. The 964/993 CCUs do have intermittent problems occasionally.
We've tested and repaired these for over 30 years for Porsche owners, Porsche shops, and many Porsche Dealers in the U.S.

pretarch

Try this Porsche climate control unit troubleshooting guide for further diagnose the CCU:
https://cdn.shopify.com/s/files/1/25...18210647334672

ToreB

This looks like a problem with the power supply of the unit, either externally or internally.
I would start with checking fuse 1. The 964 fuse holders can fail, and the high blower fan motor current through fuse 1 can cause heating and corrosion problems on the fuse. This is also the main power supply to the CCU. This web page contains info on the CCU power supplies and how to measure them. If the power supplies are OK, it could be a problem with the internal CCU power supply relay solderings. This is an easy to fix for a guy with some soldering experience.
Cheers,
Tore

systemsc

Good point, as most forget that the 964/993 CCU needs three power sources, #30 (constant power - K connector pin 2), X (accessory power - G connector pin 29), and #15 (key- on power - G connector pin 35).

vonhummel

Thank you to everyone's thoughts and ideas. Once again this forum is the best resource for keeping our cars on the road.
In looking at the pcb under a magnifying glass there was a crack around one of the terminals. I did find another post with a similar problem and appearance of the pcb. https://rennlist.com/forums/964-foru...se-help-2.html
I soldered the terminal and like magic it all works again consistently. Best I can figure, it worked when cold and then as the current flowed, heat expanded it enough to loose contact. So happy when there is $0 fix.