A/C is FUBAR. TECHS PLEASE HELP!

OK so started about a month and a half ago. A/C blows ice cold. It has had the same charge of Ra-134 for one or two previous summers and ran flawlessly. The problem is that it will run fine then all of a sudden the compressor will just click off. It doesn't come on and off like if it were low on Ra-134, it just shuts off. If i turn the a/c knob off and continue to drive for about 10 minutes and turn the a/c back on the compressor will usually click back on and i will have a/c. But then i'll get anywhere from 5-25 minutes of cold a/c then the compressor will click off again. I notice it is worse in stop and go traffic, and the a/c will tend to work for longer when driving on the highway. With the car off the compressor turns freely by hand. I mentioned this to a friend and he said something about a evap pressure sensor possible going bad? I'm not quite sure so I need to guidance here.

Causes for this
1. Low pressure, or Not fully charged system
2. Faulty AC Pressure switch, think the actual name is Pressure Cycling switch
3. Some sort of restriction

Put a gauge on the switch first to see if its cycling properly.

I had to replace the cycling switch in my car but I had different symptoms. My a/c compressor kept kicking on and off while driving down the highway. It was annoying. I know it's normal to feel it kick on every so often but mine was doing it every 10-15 seconds. Kept blowing cold though. Ford replaced the entire A/C system and it still did it. A buddy asked me if they checked that switch and, sho nuff, that was the culprit. Took em 5 minutes to swap it out and I think it's a cheap part.

Ok so the cycling switch, do we know where it is so I can look at it and possible replace?

You will find on most cars along the aluminum pressure side of the hose. Most will be very close to the valve with the blue or black cap on it. Other have them on or near the condenser.

Mine was near the firewall IIRC.

pikuoff wrote:Mine was near the firewall IIRC.

Then it would be on the condenser

Bingo

Thanks gentleman

The low pressure switch is usually on the accumulator. Paul, if you can be under the hood when this happens, check to see if you have current to the clutch. it's not uncommon for the clutch coil to get hot and give it up until it cools off. When this happens, take a blunt handle of something and knock the plate and see if it re-engages.