I hope I am in the correct place for this...

I have a '97 Saturn that the AC compressor will not kick on. I jumpered the Low/High pressure switch connector and it still doesn't engage. If I ground pin 86 on the AC relay, the clutch engages.

Any ideas?

 

I should add that I have 12 volts on the Low/High pressure switch when I push the AC button, but I still have to ground pin 86 to engage the clutch.

 

Sounds like the Powertrain control Module (PCM) is not providing the proper ground to trigger the compressor. Suprisingly, the Engine Coolant Temperature Sensor (ECTS) also plays a part in this circuit via the PCM. It's a long shot, but spend the $15 to replace the ECTS ......

 

One other note, I have not seen or heard the fan turn on yet. The car runs cool, but the fan does not come on when you push the AC button. Shouldn't it come on when you call for AC? Again... PCM???

 

Thanks OceanArcher, is there a way to bypass the ECTS just for testing? resistor etc...

 

here's an ects resistance vs temp chart


http://www.saturnfans.com/photos/sho...hp?photo=42597

 

Avalanche1 --

On your car, if you set the A/C controls for maximum cooling, and the air control to recirculate, the engine cooling fan should come on ....

 

Yea, I set A/C to Max and pushed the recirculate button and no fan. grounded fan relay and it comes on fine (Fan tests good).

 

Disconnect and measure across the contacts of the ECTS with an ohmmeter ... compare to the chart posted by DERF. If the measurement is in line with the chart, then I would start looking around for a replacement PCM

Oh, and take the jumper off the High/Low pressure switch and hook it back up ....

 

Thanks,

There are two sensors on the right side of the block (closest to the firewall). Are one of these two the ECTS? One has a single wire (Temp Gauge??) and the other two wires (ECTS??) The engine is hot at the moment, so I will let it cool down and check it.