hvac problem. help!

[monsty]

My 993's interior fans have stopped working. Compressor does not switch on either. Since i have another one, ive tried swapping ccu and final stage driverboth work fine on the other car. Visual inspection of wiring shows no damage. All fuses and relays checked. Both blower motors confirmed working. Ccu operates recirc flap but no compressor click or blower.

In short. im stumped. One part i havent replaced is the pressure switch. I know it controls compressor operation but i doubt it would cause the interior fans to stop working either.

Any ideas? TIA

[monsty]

Guess ive stumped everyone. i ran into a pinout of the ccu. Started jumping wires to manually activate blowers condenser fans etc. All worked. From what i know, there are conditions that shut off certain components such as compressor when temps are freezing but from observing on my other 993. There seems to be no conditions that shut off the blowers. Anyone know better?

I also found a 3rd feedback wire from the fsu to the ccu. Could this trigger non operation of the blower?

[JFP in PA]

My 993's interior fans have stopped working. Compressor does not switch on either. Since i have another one, ive tried swapping ccu and final stage driverboth work fine on the other car. Visual inspection of wiring shows no damage. All fuses and relays checked. Both blower motors confirmed working. Ccu operates recirc flap but no compressor click or blower.

In short. im stumped. One part i havent replaced is the pressure switch. I know it controls compressor operation but i doubt it would cause the interior fans to stop working either.

Any ideas? TIA

Start by making sure you checked all the fuses and relays, checking fuses #17 (heater fans) and 39 (AC condenser fan) in the central electrical panel; then check fuse #42 (AC compressor relay) in the engine compartment relay panel. You should also check relay #R14 (AC condenser fan) in the central relay panel; as well as relay #2 in the engine compartment relay panel.