Truck is a 2001 7.3L superduty. Here are the symptoms: The a/c blows cold air 95% of the time, but periodically, it will start blowing cabin temp air (not cold air) as if I turned off the a/c but still have the blower running. Usually, it will cycle back on by itself after a few minutes and start blowing cold air again. I was finally able to pull over in a parking lot when it stopped blowing cold air and sure enough, the compressor had stopped turning.

My first thought was that it might be the low pressure switch cutting the compressor out. But if the truck were low on freon, would the a/c be blowing cold the other 95% of the time (as mine is)? Part of what makes it hard to diagnose is that it only does it once in a while and usually only for 2 to 5 minutes at a time. Therefore I wanted to avoid taking it to the dealer for them to run up labor hours just to tell me they can't replicate it. Any thoughts on how to diagnose this? Could low freon explain the symptoms? Bad pressure switch?

 

You need to check the compressor clutch gap. Sound like the gap has gotten a little to wide and it wont engage. Check out these threads for info on getting it fixed.
Exact symptoms for air gap.


https://www.ford-trucks.com/forums/50...ml#post3818335

and
https://www.ford-trucks.com/forums/58...ml#post4464164

 

Read this:
https://www.ford-trucks.com/forums/5...ml#post4464164

Pop

 

Thanks for the great info. I feel like a dummy because I only searched the superduty forum and didn't even realize there was a separate A/C forum! Great information. However, I do have a question: When you check the clutch gap, does it matter if the clutch is engaged or disengaged when you check it? Also, I'm not 100% sure where specifically to measure the gap. Is it the gap between the large diameter disc of the clutch assembly where it abuts against the rotating belt pulley? I wish I could post a photo with an arrow pointing to where I'm talking about.

 

wouldn't hurt to check freon level too. If you have a guage, this is a quick easy test.

Strangely, one possible symptom of low freon is too cold air. My dad's old 65dodge used to get ice around the metal outlets. The mechanic checked and it was low on freon. I think the cutout makes this less common, but you could be in a "between" zone of low freon and cutout.

Low freon will cause the cutout to switch once in awhile and happen longer and more often as the leak progresses.

I never had to check the clutch gap so can't say there.

Good Luck

Jim Henderson

 

The clutch must be disengaged, i.e., the compressor not turning.

You've got the correct idea about where the air gap is.

Check the air gap with the engine turned OFF! Safety first.

Pop

 

I just checked the gap. I can slide up to a .045 gauge into the gap. Do you think that's enough to cause a sporadic problem? It doesn't do it all the time. In fact, in the last two days, it hasn't done it at all.

 

Yes, that's about when problems can begin.

Twenty-five thousandths would be a much better figure.

Pop

 

I have the same truck and just had the same problem. Clutch went out on the compressor. I went ahead and rebuilt the whole system. Cost about $600 parts and labor.

 

I would say it might be time for a new dryer also, and an inline filter...
After you fix the gap, you may want to replace those items then have the system vacuumed and charged...

Thats along time for a dryer anyways

 

Clutch spec is 0.014-0.030". Yes 0.045" is well out. Pull the clutch and take a shim out. It seems to be a bigger probelm when the clutch heats up.

If that works, you do not need to crack the sealed system and replace the drier or anything else. Clutches wear, ya know...

-dave

 

some of these has a bad connection at the Feild (magnet) might be worth a shot.

if you confirm what it is maybe I can save you a few bucks on parts so visit my site.

Ed

ps: Hi Marv and Costa

 

Okay, I did the shimectomy today. Was amazingly easy to do. There was only one shim (washer) in there. I removed it. I also measured the shim I removed. It's thickness was .039. That seems kind of thick given that the original air gap I measured was .045. So after I put everything back together (minus the shim), I measured the new air gap and found it was about .010. That seems kind of tight, but I turned the a/c on and off a few times and the clutch is doing what it's supposed to do. So I guess I'm good. Time will tell.

Thanks for the help!