I could really use some help. Car is all done, factory ac was working fine. Getting last few bugs out and now the compressor is getting no power and won't kick on. Power is getting to switch at controls but doesn't make it out to the compressor. When I touch 12v to the compressor it kicks on. Where and what am I missing? Is there something in between the switch and compressor that could have gone bad that I am missing?

Chris

chris, what year and make car?

68 Camaro SS396 big block convertible.

Not sure about stock but on my Vintage Air system there is a switch on the drier that goes inbetween the compressor and the switch inside, this switch disables the compressor if the pressure is not there from my understanding. ie your refrigerant has leaked out so it doesn't allow the compressor to run.

what brian said...the switch is there so that the compressor doesnt operate without freon, and more importantly, lubrication...the cycled feeon carries with it an oil charge thru the closed system...when there isnt any refrigerant, the oil has nothing to carry it thru the system, so the compressor will be damaged if operated without oil...it could be either empty, or the switch is bad...does the drier sweat, or any hoses get cold when the compressor is activated???

It is a suction pressure sensing switch. You can troubleshoot it by unplugging it and jumpering across the wires momentarily.

Thanks guys for the info. I'm looking for this switch you guys are talking about but don't see it. What does it look like? Where is it located? This is all factory stuff and I don't recall this switch.

Theres no low pressure switch on the old cars. There is a low temperature switch on the passenger side of the A/C box in the engine compartment. This is a normally closed switch that opens when air temperature gets down to 29 degrees or so.

Its probably one of the swiches up under the dash, either the switch on the A/C door (on top of the inner heater box) or the low blow switch on the back drivers side of the control panel. Your going to have to trace it back from the compressor coil thru each switch to find out where the break in the circuit is.

SUCCESS! Thanks to everyone who helped. Mark you were close. It was the ambient temperature switch. Bypassed it and we have ac. New switch on the way.

Thanks Camaros.net