I picked up a 964 CCU at the TRE Motorsports moving sale this past weekend for a very, very low price. I bought it only to get a replacement A/C button since my original button broke.

Is there anyway to bench test a CCU to verify if its functional? Something a DIY'er could do or does it need to go out to a specialized shop? Im not really interested in swapping CCUs in my car for fear of shorting other things. What would be an average cost to test & verify the units status? Is there a local shop in SoCal?

If this thing works then I may just offer up it up to the community for a great price - minus the A/C button.

 

http://www.systemsc.com/

 

It is pretty easy to bench test an AC controller if you don't mind spending a lot of time. I have not done it on a 964, but have several times on Mercedes using a very similar system. You need the chassis wiring schematic to figure the pin assignments on the connector. It helps if you can get your hands on a salvage yard connector to break out the lines. After that, it is simply a matter of connecting resistors to simulate sensors, and switches to simulate contact closures. You should then be able to observe the action of the unit to see which functions operate correctly, and which do not. Repairs on early generation units are fairly easy. Later versions have micro-processors and multi-component single-in-line packages for components. It gets quite a bit more complicated. Surface-mounted device circuit boards are pretty much throw-away items since they are cheap to make but difficult to repair.

Checking function is the same regardless of generation, but they seem to pick up features like the vent servos as you get to newer cars.

 

If you end up parting out the CCU I would be interested in the recirc and defrost buttons if they are good.