AC not working...again.

[CapitalMark]

So, 02 yukon 5.3 with 323,000 miles on her. Air conditioning hadn't worked for a while, I unplugged the battery and re-filled coolant and all was good for 3 months. All of a sudden 2 days ago she stopped working. Connected the pressure gauge that came with the coolant filler, and the pressure showed in the red. The compressor hasn't kicked on at all since she stopped working. Any ideas?

Thanks,

Mark

 

[Tahoe0159]

Those single gauges on the cans at the auto stores and Wal-mart are fairly useless.

There are threads on here that help you diagnose AC issues.

Most will tell you that to check the compressor and freon level, you really need a dual gauge set.

I just bought an AC gauge set from Harbor Freight (Autozone has them too), which is really is the minimum that you need to properly check the freon level, because you need to see the pressure on both high and low side while it's running.

Autozone has free diagnostic video on Youtube that explains what the various pressure levels mean.

https://www.youtube.com/watch?v=UW1GDiOa0kE

Also, have you checked to make sure the AC fuse is good?

You may also need to check there is good voltage to the compressor clutch. If the wiring is worn out, or the connector bad, you won't get any cycling, regardless of the freon charge level.

 

[CapitalMark]

Thank you. I reset the battery and can hear the mixer turn when I adjust the temp. I'll try going by auto zone to get a pressure gauge. I appreciate you replying.

 

[Tahoe0159]

I would watch that video on youtube, too.

Autozone has a whole series on automotive AC that I've found very helpful.

 

[clandr1]

Sounds like you have a slow leak somewhere. Over time the o-rings can go back and let the R134a seep out. Hopefully that's all it is, and you don't have a leak in a hard line or evap/condenser.

Next time you charge it with R134a, use cans that contain UV dye, and get a decent UV flashlight. You should be able to spot the leak pretty easily.

 

[Tahoe0159]

If the compressor is starting to go, you can also get high pressure on the low side and low pressure on the high side.

At that many miles, if it's the original compressor, would not surprise me.

Here is a really good link to an Autozone Diagnose Common A/C Problems web page.

http://www.autozone.com/landing/page.jsp?name=diagnose-auto-ac-problem


Read through that page and use the "next" button. It's pretty thorough and if you do all of that, you will very likely know what is wrong and how to fix it.

You will also probably know if you want to tackle it yourself...or not.


If you don't want to spend the time learning to diagnose with the manifold gauges, or don't feel comfortable doing that (and I wouldn't blame you...this is a specialty area) , then I would recommend taking it to a good AC shop (who specialize in AC) and have them do a diagnosis. Should not cost very much and it will help you decide what you want to do.

Best case, It might only be the compressor clutch slipping (which is cheaper to fix than a new compressor) or even an AC belt that is too loose or slipping at higher RPM.

 

[CapitalMark]

Found the problem. The compressor drive belt disintegrated and came off. Now just hope the belt didn't burn up from the compressor being seized.

 

[TheAutumnWind]

Glad you found the problem. good luck!

 

[Tahoe0159]

Worth getting a new belt and putting it on to see what happens.

We will hope for the best!

 

[scoobyxj]

Also you should be able to spin the pulley very easily with the truck off. Turn the key on (but don't start) and turn on the AC. You should still be able to turn the compressor by hand although it will kinda hard to turn. If its hard to turn with the truck off then the bearing on the pulley is bad. You can replace just the clutch, pulley, and magnet, but at your 300+k I would really recommend just replacing the whole compressor. The clutch kit is like $150 on Amazon, and a compressor only is right around $200. Another $50 will get you a new orifice tube, and receiver/dryer. Which really you could get away with not replacing as long as the compressor itself didn't go bad.