My A/C quit blowing cold on me today. I was driving in traffic on the freeway, I turned it on, everything was fine for a couple of minutes, but then I realized the air was getting warmer, to the point of it felt like the compressor wasn't going at all. I checked all the controls, they were set fine. I fiddled around with turning it on & off, adjusting the temp. control, etc. I got the air to blow cold again once for about a minute, then it quit again.

After I got home, I checked to see if the clutch was actually engaging, but it wasn't. I checked the fuse, looked ok, but replaced it anyways, still no compressor action.

Two subtle things I did notice, the compressor tried to kick on a couple of times for a millisecond, I could hear it & saw the clutch make about 1/10th of a revolution, so it seems like power is getting to the clutch. Another weird thing was that the engine idle with the A/C on (but not working) would go up & down on a regular cycle, like about every 3 seconds, kind of like a load was being applied & then taken off. Turn off the A/C & it idles nice & steady.

My guess at this point is that the clutch on the compressor is bad. If that's the case can it be replaced without replacing the whole compressor? What other likely fault could be causing this problem?

After researching Mustang problems on google, it sounds like there is a low pressure sensor that can keep the compressor from engaging. I think I see what could be that up front, I was going to try to jump it for testing purposes. Anybody got more info about this?

Edit: So I guess I found the pressure switch. I pulled the connector off, seems there are 4 wires on that. Can anyone give me some color codes or pin outs as to what ones I should jumper to test? With the conn. disconnected, the idle rpm variations go away, so I think I'm on to something with this pressure switch. Now I'm thinking either the sensor is bad, or I somehow lost pressure in the system. Either way it sounds like a trip to an A/C specialist, even if I just need to replace the sensor, I'm guessing the freon needs to be drained first or otherwise it will drain out by itself as soon as I remove the old sensor .

Well, the switch I found up front was maybe the Hi Pressure switch. I found the Low Pres switch back by the firewall. Only 2 wires on that, jumped it & comp kicked on, so I bought a new switch (at the Ford dealer), now everything works ok again .