[Alan in AZ]

Yes you are now on the right track. Lets stop calling an AC Compressor a Cooling Motor - someone is not helping here - I think they were answering a quite different question on the cooling fan? (nothing on your 928 is called a 'cooling motor' you have a Compressor & a Cooling fan which are of course very different things).

Power to your AC head unit also supplies the AC Compressor Clutch - This power is supplied via Fuse #9. Power enters the AC head unit on its pins 4R & 5R.

A switch in the head unit slider connects power to the evaporator freeze switch (located in the bulkhead area under the cowl - on the Air plenum). The slider switch output exits the AC Head unit on its pin 9L as a Violet/Yellow wire and travels through a single pin connector to the Freeze switch. (need 12V+ on both switch pins for AC active).

From the Freeze switch it is connected (another Violet/Yellow wire) to the Central Electric (fuse/relay) panel on pin J2 (on bottom connectors) from there is just connects to pin Q2 (no other internal connections) and exits as a Black wire (in a loom) to the low pressure switch mounted near the AC dryer. This loom goes through the firewall grommet and runs under the (LHD) passenger fender lip to the front.

From the low pressure switch (open when refrigerant pressure is too low) a black wire goes back to the 14 pin connector (also via the loom) on Pin 9 and carries on as black wire (now in the engine loom) to a single pin connector where it splits to two black wires; one to the Compressor Clutch and one to the Supplementary Air valve (for AC active idle compensation). The final leg to the compressor should have another single pin connector where it switches to a red wire (the final leg to the Supplementary air valve stays a black wire). These two single pin connectors should be near the loom & near the AC compressor...they may have been ripped off... if so you can run a new line direct from the 14 pin connector to the AC compressor clutch(its quite close) - however you must also find & connect up the supplementary air valve or you may stall at idle with the AC on - you can find that later of course...

Central Electric Pin Q3 on your car is not related to the AC clutch - only the Cooling fan. You do need this to operate correctly for AC (and engine cooling), but its quite independent. If your cooling fan works normally in driving - then don't worry about it for now - until you get the AC compressor working.

Alan