Avenger6

OK, just spent about an hour looking through old threads, not yet finding specific info on this situation: I have just recently started getting only HOT air from center vent, no matter where the temp **** is set. If I turn on A/C, it will got from HOT to WARM, again, no matter where the temp **** is set. With A/C switch ON, and temp **** to coldest setting, the side vents will put out fairly cool air, but not cold.

Any Ideas? In the 944 I used to have, this would indicate that the CCU is fooked. All threads here seem to say that the CCU on 993s is pretty reliable with few failures.

Any comments, thoughts, or links to old threads much appreciated!

Ron

I'm not sure how the air is directed on the Porsche. I know on at least the older Merecedes vehicles the air is controlled by vacuum control modules in the dash. When the air doesn't come out the center vent that module need to be replaced and requires that the whole dash be removed to do so. It's not a pretty siight.

Hopefully our Porsches don't have a system like the MBs.

epj993

I had just the opposite problem - no heat/defroster on the passenger side. Turned out to be the electric motor on the heat mixing valve in the passenger footwell (there's also one on the drivers side). Yours may be stuck in the open position.

It's fair easy to check. You can disconnect the valve from the heat tubes and watch its operation. The valve should open when heat is turned up and close when turned down. The electric motor is a seperate part screwed to the top of the valve.

One other possibility would be the temp sensors - there are two located in the HVAC assembly in the trunk. I don't recall the exact post, but search for 'HVAC'.

jimq

I had the exact same thing. Check if the center servo is moving when you turn to hot. If not try cleaning the contacts where the plug goes in to it.

Avenger6

The plot thickens!! OK, some more playing around yields the following info:

The lower outborad dash vents are giving different temps, which leads to the mixing valves, about which there is good info on other threads. Question is, does the center vent get its air from the right side mixing valve, or does it have it's own?

I'll keep digging.....

Avenger6

Partial (Maybe complete) diagnosis! The passenger side "Temperature mixing flap (p. 80-5 and 80-6 in Section 8 of Diagnostics) of the workshop manual doesn't move when turning the remp dial. Drivers side does. I'll swap them first to see if it is in fact the servo.....

All knowledge IS in the archives! One must be persistent and creative with the search engine!

epj993

Sounds like you're on the right track. It's probably the electric motor, not the valve itself as it is a pretty simple device and not likey to fail. BTW, the motor runs about $100 from SunsetPorsche.com.

Good luck!