Last month (December - winter in NY), I purchased a 1991 Cab C-4 with 34, 600 miles. Unfortunately, the Climate Control does not work properly. The symptoms are:
1) Constant heat from driver's side & middle vents. Far right passenger's side vent blows cool air.
2) Round thermostat dial (blue & red dots) does not work.
3) Slide Controls appear not to work.
4) Blower fan 0 to 4 does work properly.
5) Defrost button engages & blasts air through vents not to windshield.
6) A/C button turns on (yellow light) but the condenser/compressor appears not to engage -- no change in RPM's, etc.

I have Adrian Streather's 964 book & it appears that the two mixing chamber Servo valves under the front hood may be bad. Any other ideas?

Thanks. This is my 1st post!

Pete

 

Do a search for "CCU" You will find a lot. In case you need a new CCU send me a PM I have a extra one that is working fine.

 

Welcome to our happy Rennlist 964 family. Unfortunately, the CCU is one of the more "interesting" systems to diagnose. The servo's do go bad, and if there is a problem with the electric blower on the engine, the blower fan, and temp ***** will not appear to work. To start, if you turn the thermostat to the blue dot, does the blower fan **** work?

 

Burgass & Eric,
Thanks for the reply & offer!

When I turn the thermostat to the blue dot, the blower fan (0 to 4 speeds) does work fine.

Thanks,
Pete

 

In the engine area, on the left there is a fuse box, check the fuse for the rear blower....... if it's blown, the inside blowers will not work when the thermostat setting is off the blue dot.......

 

Eric,
After driving the car yesterday, I turned off the ignition & then turned the key in the accessory position. I could hear the rear engine blower fan running... is this the fan your'e referring to?

If not, I'll check the fuse box tomorrow.

Thanks,
Pete

 

Yes, that is the fan i'm referring to......... sounds like it's not the fuse....... if you search through the forum, there is more debugging info..... but it sounds like your fuse is good......

 

I bet it's the servo. You can try to fix it yourself. See www.porsche964.co.uk - check under technical / electrical.

Geo