Last few days have been triple digits. Get in hot car with A/C on auto. Goes full blast like it should. All blowing cold.

Then along my 1 hour drive, it will mysteriously stop (not just back off as set temp is reached) for a minute or so...then start back up, having to go back to aggressive cooling. It's like something goes beyond spec and into limp mode. Or could the temp sensor(s) be giving false data then come back online?

Ideas?

2005 Z51 manual FWIW

 

You have manually set the temp right, you're not using auto?

 

Auto with thermostat preset at 72.

I'll add that the first time it happened I adjusted it down a couple degrees and it came back on. But it may have just come back on regardless.

 

My 2005 had A/C problems. One issue was a factory coolant overcharge but what ultimately ended up being the biggest culprit was the condenser coils were so jammed up with road debris that it was barely passing air. It was so bad that my engine coolant temps were elevated as a result because the condenser sits in front of the radiator up front. I had the condenser replaced, new inline filter, and new compressor all done in one shot and now it runs flawlessly all the time no matter how hot it is.

Before: intermittent AC that was constantly cycling on/off when it was above 85 deg F outside and coolant temps that got as high as 235.
After: rock solid AC that never cycles off even in 100+ deg southeastern summer days and my coolant temp is usually about 200.

Photo of just how bad it was. This was AFTER debris had fallen off of it once after it was removed.

No wonder my AC performance was awful and my coolant was running hot.

 

High pressure switch kicking the system out.

As stated, check the heat exchanger raditor to make sure it clean as well the radiator its bolted to, then may have to have to pressure test in the system to make sure it not over charged.


Or, could be the in line filter in the system clogged up, and what is causing the high side to go over pressure instead.


Note, if the in line filter is the problem, Freon will need to be salvage, fitter pulled and replaces since it in the line/bock on the heat exchanger, system vacuumed to pull any humidity out of it from is being bleed down, the system re-pressurized to the correct amount of pressure.

If you have your own A/C pressure gauges, then here are the charts to download to check pressure amounts in the system when it running.

http://www.mediafire.com/file/6hw61h...harts.pdf/file

 

Have had the car 7'ish years with no A/C maintenance, so I'm sure it's not overfilled. I'll take a look at the heat-x. If it needs more, I'll have to take it to a shop. I don't know shinola about A/C or have the tools for it.

So either of these (heat-x or filter) cause it to kick off for 30-60 seconds and back on? Would the filter issue be affected by ambient temps/extended run times?

I'll take a look at the coolant temp too. I honestly didn't look during the issue. Was on the highway, but did seem to be associated with a change (lower) in speed as I'd come up on some traffic.

 

As stated, there is High pressure senor on the high pressure line, and when the Freon high pressure gets too high, will kick the system off before it blows a line.
Hence as the Freon gets higher, it increases in pressure and why you can't over pressure the system to start with.

So could be heat exchanger raditor that is blocked and not allowing the Freon to cool back down, Radiator behind it clogged and not allowing enough air through the heat exchanger radiator in front of it to flow through correctly, or could be the in line filter clogged instead that is causing the problem.

Heat exchanger radiator is not hard to pull forward in place with the lines still connected to pressure wash throw it back side, as well as the radator back side to get them clean of debris. Also, look in the front of the heat exchanger from the under the car, since you can such up a lot of debries/trash bags to block it from the front side as well.

As for in line filter if clogged up, since its in the lower bunge that the line goes to the heat exchanger, system has to be drained to get to it, then system vacuumed to pull any humidity out of the system from when you had it open, then re pressureized ( and again, to the correct table pressure since if the system is over charged, it going to cause the high pressure switch to kick the system out).
Hence here you just need to get gauges on the system with it running, and will be real simple to see the clogged in line filter since the differences between the low and high pressure sides are going to way out of wack to start with.

 

Everyone is picking up on the high pressure cut out switch but there is also a low pressure switch. It is important to know if the original factory refrigerant charge was ever corrected.

 

If you have a gauge set it would help to have some readings, but my guess is some sort of blockage leading to the system over heating or sensor being triggered. I also wouldn't rule out just low refrigernt.

 

Condenser/heat-x looks pretty clean and no garbage. I guess it goes to the shop as I'm not versed on A/C. I'll try to log water temp if/when it happens next time. Ambient is significantly cooler now so.......