I have 1992 dodge pickup. A/c not working. Fuse is good. Checked sensor on side of h valve and compressor will work if I ground one of the two wires coming from the sensor.
Mopar or no car.

 

Check the A/C relay on the drivers inner fender. Think it's the one closest to the firewall. But double check by going up to "The Sticky" at the top of the forum, go down to electrical, and look for a thread called..."What are all these wires on my intercooled motor"...or some such thing.

 

That switch on the side is the low pressure cutout switch, are you sure the pressure is good? Have you put a set of gauges on it? Does it blow cold? If all is good, the low pressure switch may be bad or the wiring is open...Mark

 

The weird thing is that if I jumper the plug to the low pressure switch like some people suggest with a paper clip it doesn't start the compressor. I have to ground one wire on the plug to get the compressor to start. Then it runs and cools until I remove the ground.

 

So do you think that is a possible bad relay.

 

You will need to check voltage. As I recall the pressure switch is a really a switched ground.

With pressure, the switch is closed. Sounds like you have a broken or disconnected ground wire.

 

Did a couple of checks as you suggested. I checked voltage at the plug and had 13.9 volts. I checked the low pressure switch and it was closed. I have looked for a broken ground and as of yet I haven't found anything. Do you have any other suggestions.

 

Trace the wires from the connector to thier ends and do a continuty check. Wires can be broken internall without showing damage to the casing.