[usnzt84]

HI guys. im new to the 5.0 forum. usually in the 05-09 forums. but i have a 92 LX and the A/C doesnt work. It worked last year so my first guess was to charge the A/C. well while doing that i noticed that the compressor never kicks on. so i checked the plug going to it and there is no voltage. So go figure it wont kick on. anyway i have a haynes manuel and started chasing the wires. fuses are good and the wires from the fuses to the A/C control panel are correct, but from there on all the wires are not correctly color coded with the book. so i am lost. i dont know where the WOT relay is at and i really hate chasing wires. can i get any help??? thanks in advance.

[1989Gt.]

yeah chasing wires in this car is like a damn mission and a half, are you sure its just not a faulty compressor.

[usnzt84]

not 100% sure but when i test the wires going to the compressor they dont have any power. it should have power with the A/C running right?

[mustangbrad94gt]

unplug the low pressure switch (located on the dryer) two wire plug, put a jumper wire across the plug terminals, if compressor will kick on- your low on freon, you have a leak some where, It only takes about 10-12 ounces of freon to open the low pressure swith, which will give an open circuit to the 12 volt supply to the clutch, this is a safety device to protect the compressor if your freon is to low, if the jumping of the low pressure switch does turn your compressor on, dont let it run long, minute or two, add some freon, your leak might be small, 1 can could last all summer, just have to see, when charging low side, if using r134 charge to a head pressure around 225#, low side should go to about 30-40, let me know if you need more help

[usnzt84]

thanks ill try that

[95StangMX]

Originally Posted by mustangbrad94gt unplug the low pressure switch (located on the dryer) two wire plug, put a jumper wire across the plug terminals, if compressor will kick on- your low on freon, you have a leak some where, It only takes about 10-12 ounces of freon to open the low pressure swith, which will give an open circuit to the 12 volt supply to the clutch, this is a safety device to protect the compressor if your freon is to low, if the jumping of the low pressure switch does turn your compressor on, dont let it run long, minute or two, add some freon, your leak might be small, 1 can could last all summer, just have to see, when charging low side, if using r134 charge to a head pressure around 225#, low side should go to about 30-40, let me know if you need more help

REPS to the Newbie for good advice and not just blurting out BS

+1 was going to say to check this, I have had both of my work cars (new PT cruisers) go out within about 3-4 months of buying them, they now have paperclips in them and electrical tape. The freon is fine and I don't have time to take them to the dealership to get it fixed and they are the only ones around here that sell the switch and if they dont install it, they say my warranty is void....

[91sleeper]

yep that is correct advice right there.

[usnzt84]

ok guys. where the hell is this plug at on the car?

[03SonicBoom]

Originally Posted by usnzt84 ok guys. where the hell is this plug at on the car?

On most vehicles it's on the top of the dryer canister.

[usnzt84]

OK, i jumpered across it and the compressor kicked on. i added 2 cans of "freon" and then pluged it back to where it was. still the compressor does not work like it should. it got nice and cool while the compressor was running. but as soon as i pluged it back in, nothing. the plug had verdagree on it. green and all. i cleaned it the best i could w/out coke. can the thing it plugs into go bad?

[03SonicBoom]

Originally Posted by usnzt84 OK, i jumpered across it and the compressor kicked on. i added 2 cans of "freon" and then pluged it back to where it was. still the compressor does not work like it should. it got nice and cool while the compressor was running. but as soon as i pluged it back in, nothing. the plug had verdagree on it. green and all. i cleaned it the best i could w/out coke. can the thing it plugs into go bad?

Yes, the low pressure sensor switch can go bad. It sounds like yours is shot.

[Mr_John_Doe]

It would be nice if usnzt84 updated everyone on what happened.

That said, I just wanted to thank mustangbrad94gt for the excellent advice. I wanted to point out to everyone that when I Googled "Mustang GT Air Condition" this one was of the first sites to show up in results. Well, for the benefit of everyone here as well as anyone else that may be Googling this, I had a very similar issue with my 99 Mustang GT's a/c.

The a/c was cold, but I noticed the compressor was cycling too often and the engine RPM at low speeds with air on was a bit erratic. Well, a few weeks later, the a/c was blowing hot air. When I looked under the hood, I noticed the compressor was not cycling. In order to find out if there was *any* pressure in the system, I hooked up the low side (near firewall) and high side (near radiator) a/c ports to a Harbor Freight manifold gauge kit. The pressure on the low side was over a hundred pounds. This reading meant two things to me... a) first of all, it meant the system was under pressure and had freon and b) it meant that the compressor was not cycling for some reason, because when it cycles, the pressure would have been much lower.

At any rate, that's when I did some Googling and found this site and found your info about the "low pressure switch." To be more precise, it's a Low Pressure Relay Switch. The bad news is that (except for maybe Rock Auto) it's basically a dealer part. The good news, is that it was less than $20, it's extremely easy to reach and replace, and IT WORKED! I noticed that the Relay has a small circle with a stylized cursive "GE" stamped on the inside of circle, so it appears this part is actually sourced from General Electric. I'm guessing rather than Ford manufacturing its own relays, they just sourced it from GE.

To complete the story, once I installed the Low Pressure Relay Switch, the compressor kicked on, immediately. Once the compressor was on, I was able to add about a half can of freon to the Low Side port. Now, not only does the a/c work like new, but there are no cycling issues and the engine RPM is rock solid.

Again... thanks everyone on this website, and I hope my info is able to add some info for others with the same problem.