I can't remember if I posted a while back about this. Anyway, last year I guess, my system was replaced. New compressor, dryer, flush...and new fan clutch.
I have a very specific problem that seems to happen (or be VERY noticeable) when the AC is on 'outside air'. When its hot out, and driving or idling, the AC seems to blow at 45 degrees. However, if I stop at a light for more than a few seconds, and then drive off as normal, the AC stops blowing cold. It blows air like the compressor is completely cutting at. As long as you are accelerating (slow or fast) the air gets hotter and more humid. After you get to cruising speed for 15-20 seconds or do, you can physically feel the air get dryer and colder like the compressor kicked back in. It doesnt happen every time, but it happens a lot.

It went back to the dealer that did the work, they checked everything, recharged to spec and said everything is fine. It actually went back there twice after the repair and each time the numbers checked out. I took it to an independant shop and they kept it for two days and said everything looks and operated fine. Im guessing they simply cannot duplicate the problem that causes it to do it. The pressures check out according to them as well.

Basically, it seems like it might be a clutch gap thing, but the compressor is brand new...and I assume it comes with a new clutch. LOL. What else can cause this? Im certain its unrelated to charge since Im blowing 40 degrees driving on 100 degree days....but no one can seem to fix it and its a little irritating. Any ideas at all? Anything?

Is there anything I can check? At this point, the work is out of warranty and im pretty much in "wait until whatever it is completely fails" mode....which could take a LONG time.

 

Try replacing the low pressure switch.

My 01 went intermittent on me last month. I noticed it would sometimes drop out (got warm and humid) and sometimes went frigid cold (thermometer said mid-20s). I ended up stopping at an AutoZone while on a fishing trip with my wife and replaced the switch ($15) in the parking lot with a pair of common pliers.

You could also measure the clutch gap to see what it is rather than assuming it's good since the compressor is "new". I learned a long, long time ago the hard way that "new" doesn't always mean "good".

 

Im certain that was replaced many many miles ago for almost the same condition. I guess I kind of assumed they replaced that switch when they charged me my ***** for the repair work.

Can this part be replaced without evacuating the system? Will I lose freon when I unscrew it?

 

There's a Shrader valve under the switch.

 

had a similar problem on my 04 after the same repair. Solved a year later when the water pump went. New pump solved the problem. I think it was related to a water flow issue.

 

That doesnt make sense to me. But Im not replacing that bad boy until it fails completely even if it was the case. The water temps according to my scanguage are right where they should be.

 

The water pump doesn't have anything to do with the A/C's ability to cool and condition the air.

 

It does the rad fan clutch, which then does the A/C system.

Once the water pump failed, worn fins insufficient flow, and was replaced, my A/C system then returned to normal function. No longer cutting out at stops and blowing worm when rad clutch engaged.

 

A few other things, first if there is a switch on the accelerator system that cuts out the A/C when the pedal is down it could be adjusted in too far. Or inside the dash the door between the two could be opening or closing due to a vacuum loss.

 

electronic in powertrain control

 

Seriously???

At least please learn how the system works before trying to tell someone how to troubleshoot

 

Yes seriously. I know the basics of how an A/C system works. Both of those issues are common. I did auto A/C work for many years. So at least learn what experience someone has before you call them out.

 

Neither of those conditions are even possible in a Ford truck of the vintage under discussion.

1. There is no switch on the accelerator system so there is nothing that can be out of adjustment.
2. The temperature blend door is electrical, not vacuum operated, so a vacuum issue can't cause any temperature-related issue.

Like I said, learn the system under discussion, otherwise you'll just waste the time and efforts of the person trying to fix their system by giving them information that's way off base.

 

Go back and look at my post again and see that I said IF. If it has a vaccum controlled door OR main control in the dash it can loose vacuum. It's not a diagnosis it's a place to look just in case. get off my case. I do know A/C I did it for many years.

Many vehicles have a system that cuts out the compressor at WOT whether it be electrical or manual. Again not a diagnosis just a place to look.

So don't be telling me to learn anything. I know plenty about A/C and many of the typical issues that cause the problem he mentioned. Just trying to help. So get the F off my case about it.

Telling me to "learn the system before commenting" is out of line in this case.

 

I did replace the LPC switch. The problem is still persistent. The fan clutch was replaced during service with the rest of teh the AC. I did put gauges on it, and at 1500 RPM we are sitting at:

L:45-47
Hi: 275-300

This indicates to me (and the AC techs that have worked on it) that the issue is completely unrelated to refrigerant levels. I am not sure since that is not my forte, but After all this time, Im wondering what else can cause it.

To be clear, the AC works fine at stop signs and idle. Its when you take off....about 10 seconds after you take off, the AC goes warm, then it will eventually level back out where it was. I don't have any clue what else can cause it but I dont think its normal.

The only thing left to do is tape the gauges to my windshield and go for a ride.....Im out of options now and it must take a technician that is pretty special because the ones Ive talked to have no clue.