AC Stopped for first time in 10 years, then worked again

[graycenphil]

New member here and the forum looks great. I searched, but found nothing quite like my problem.

I've owned the car, 2006 Jeep Liberty for 10 years and the AC has always been great, and very cold. Today (95 degree day) it started off fine, but after about 15 minutes was noticeably warmer. After half an hour, I had the fan on high and the interior was pretty warm. Air was still cooler than outside air, but not much. After an hour or so, it got a bit cooler again, but not like normal.

Parked the car for 3 hours, and when I dorve it again for 10 minutes, the air was pretty cool. Maybe not fully cold, but it's hard to tell and it was definitely comfortable.

3 hours later, we drove home. It seemed pretty comfortable, but may not have been as cold as it used to be. Hard to say because now it is night and not so hot outside.

Any ideas on what's happening?

Thanks.

[GM Tech]

Next time it is blowing hot and it should be cool-- stop, pull over, keep engine and a/c running, pop hood, look at front of compressor- is it turning? If not, bump it with a wooden hammer handle. If it engages, starts running, you have an air gap issue, that is too wide.

Does it normally cool when first tried each day, then later on after engine is hot, the a/c quits? This is another big hint- magnetic coil resistance is greater when coil warms- such that it has trouble pulling in a clutch armature when air gap is worn too wide. When cool it can do it, problem always starts happening after coil gets warmed by engine heat.

If all above are true:
most shops would merely replace the compressor- we here recommend removing a shim behind the clutch driver to "narrow" the air gap....simply remove the driver- wiggle it off the splined shaft, look for 1 or 2 shims behind the driver, throw the thickest one over your shoulder and replace the driver- and be cool for the next 100k miles.....

[graycenphil]

Thanks GM Tech; I will look at that today. It makes sense, but would it cool somewhat if the air gap is too big? Wouldn't that stop the compressor from running at all? It was continuing to cool, a little bit, for about an hour.

[GM Tech]

When air gap is marginal- just hitting a bump, slamming hood can jarrr the clutch into action...so you may be on the ragged edge- of running, not running....

It can shut off due to normal cycling, but not come back on until next highway bump......

[graycenphil]

Thanks GM Tech. I couldn't bump the clutch - it's under the engine and behind the fan - but you got me on the right track. I tried jumping the cutch relay and it engaged fine. So I started poking around, changed the relay, then tried jumping the low pressure sensor (the one on the drier). This made the clutch engage.

I also put gauges on the system and got 45low/245high, so I think the charge is good. I couldn't find exact specs for this car but it seemed about right. So I'm thinking the sensor is bad. Am I making sense?

Two questions: Do you agree the system is fully charged?
Will unscrewing that sensor release R134, or is it just a simple replacement?

Thanks again.

[bohica2xo]

Just check the clutch gap, and adjust it if needed.

With the engine cool & OFF, check the gap with a business card. If it is wider than the thickness of two business cards, it needs to be adjusted.

Regardless of any other system issues, the clutch gap needs to be in spec. Adjust it. eliminate the #1 cause of the issue you are describing first. Then you can chase electrical issues if the problem remains.

[GM Tech]

The ONLY way to know if system charge is correct is to extract and weigh the charge that is in your system-- case closed..

[graycenphil]

Update: Seems it. was the low pressure snesor. I jumped it, and hte clutch engaged. So I replaced it, and system is working normally. Thanks again for all the advice. Great forum.