2005 Ford Freestyle AC Issues?

We have a 2005 Ford Freestyle we bought 3 years ago and have always had issues with the AC. This summer I decided to have it looked at by a mechanic in town. They replaced the Compressor and the valves and charged it up. It was better, but still not quite right and got worse as the weeks went on. We took it back and they said there was a leaking shrader valve which they replaced. It's better, but still not right. It's cold at high rpms, but warm at low rpms. I had it in park and sat in it for a while, came out warm (82 degrees outside). I revved the engine up with it in park and the ac got cold. (Around 2500-3000 rpms). Let off the gas and the ac started blowing warm again. I'm taking it back to the mechanic Monday, but he s uncertain as to what would cause it since he s already replaced so much. I wanted to know if anyone has experienced this before and what they changed to fix it. It seems that both of the fans are running, but only the right 1 is pulling a lot of air through the radiator. The left 1 is working, but not pulling much air. Could this be the issue? I'm just stumped and frustrated after spending $1,200 on it this year.

Try replacing the antifreeze and thermostat first along with any worn looking hoses, also the air filter

Left fan not pulling? There's your problem.: LH side of AC condenser blocked by leaves, etc. Possibly your radiator, too. Does car run hot? Brush it out, user a garden hose to back blast the stuff out too.

If it wasn't that, Id say, get a New AC tech. If he replaced a Schrader valve, he purged/recharged system. So it Could be low under his warranty if it leaked, again. Not if its compressor.

The system sounds like it is still low on 134a. Use a can of 134a with a sealer in it.

So, you keep giving the same mechanic who doesn't fix it more money? Kinda explains the problem.

Ford trucks from that era have a common problem with A/C clutches slipping with wear, intermittently working at certain RPMs or times of the day/temperature outside. The fix there's to get a shim kit that slightly re-tightens the clutch engagement by accounting for the lost disk thickness. Don't know if the Freestyle used the same kind of clutch that could be shimmed like that. Could be the relay to that condenser fan, some experimentation could rule that in or out, The condenser fan itself could need replacement if its RPMs at idle seem slow.