i have a 94 SLS, last summer i installed a new a/c compressor, orifice tube, and dryer, evacuated it, and it was perfect...this summer all of a sudden, the compressor doesn't work, but i have plenty of freon int he system, with the car off its equalized at 110lbs, at one point i jumped a straight 12v to the compressor and the a/c worked fine......ONLY...the 2 engine fans do not engage and run....the cooling fans only engage at low speed when the engine hits 225 degree's...but don't come on at all when i have the A/C turned on. question? is there a central relay on these cars that operate the compressor and the hi-speed side of the fans?...i have power to the low pressure switch, and power out of the low pressure switch, but no power INTO the compressor....i have no wiring diagram of the system to tell me where or how the wiring is routed...any help would be greatly appreciated...on the later news...at one point i was able to bridge the low-pressure switch connector to activate the compressor, but allas, NOTHING is working again...also...the diode box thats on the harness to the compressor, does this have anything to do wtih that?...and also at one point the vehicles DIC said low refridgerant...but now it doesnt?...this car is a woman!

Clear the codes and see if it works. See the Northstar section for reading codes. Just unhook the battery for a few seconds to clear.

110 sounds reasonable not running but I havn't remembered to test one that's charged to see what it really should be. If clearing the codes starts it you'll want to check in case it is low.

The diode is to eliminate a spike when you shut it off.

Check the pressure while it is running with a good set of guages (high & low side). Sounds like you are low on freon or the low pressure switch may be bad. The fan relays are between the fans.

its got a full charge, 250 on the high, and 35 on the low as long as i keep a water hose on the condensor, cuz the fans are not coming on at any speed with the a/c on until the engine hits 230....

....as for the Low Pressure Switch off the accumulater...the red wire in is 12v anytime the a/c is on...the green wire is the field wire which only gets hot if there is pressure in the low side line...with the key on, and the motor not running, with a/c on...its 12v into the pressure switch, and 12v out on the green wire...so that eliminates the Low Pressure Switch...plus i replaced it already...cheap part, heh...its just wierd now, no messages on the dash, no CEL's, i have the A/C turned on...theres no compressor working...no power TO the compressor, but theres power from the low pressure switch, and the electic fans aren't working....

...aren't the elec fans s upposed to work...100% duty when the a/c is switched on?

it has temporarily started to work again...the fans blow on high, the a/c is cold...and all is well....the cadillac dealer said the pcm controlls the fans, and engages the compressor, and that there was no relay? b/s? probobly!...but never the less i can't find ANY relays inbetween the 2 fans!...there is NOTHING! 2 fan's with wires leading into a taped up loom...im sure it will quit again just as fast, but i did a pressure test and left the gauges on over night...did not drop 1 lbs....in any case, any other idea's or thoughts are greatly appreciated...the caddy dealer said that the a.c. controll head *the in dash part* contained all the relays, and switch's for the fans, and the a/c compressor...im so lost, no one wants me to know jack about this car!...i've installed a/c into cars that were not offered with a/c from the factory, and a cadillac is causing me to lose my hair!...GRR

It sounds like you REALLY need a FSM at this point. Check Ebay.

what is an FSM?....i have a nice mac tools scanner...:-D

Service Manual

FSM = Factory Service Manual. It will have all the wiring schematics and trouble trees aka chase-around charts.