Need wisdom on right questions to ask about A/C issues

[A Ransom]

2000 GMC Yukon, 5.3L V8 SLT

Had A/C Compressor replaced 10 years ago. (A/C was ice cold with absolutely no problems)

Present - Compressor shuts on and off randomly.

It often shuts off if I leave the engine on while parked after 5 or 10 minutes.

After this the compressor will not come back on for a few days no matter how often I turn the A/C on/off while driving.

I took it back to the repair shop that replaced my compressor 10 years ago.

They told me the compressor was fine and that I had a leak somewhere. They filled it up with Freon and told me to drive it for a week and bring it back since they had placed dye in the system to evaluate where the potential leak(s) is/are.

When I picked it up the compressor still would not engage. However, after leaving work later that night the A/C compressor engaged and blew cold air. The next day (stupidly) while working on my interior I turned over the engine and had the A/C blowing. The compressor cut off after about 5 minutes and would not come back on.

Assuming I might have a bad AC compressor relay I bought a brand new relay and replaced the old relay and 10 Amp fuse to see if this would correct the problem, nothing.

For the past few days my compressor comes on and goes off at will and there is nothing I can do to trigger it to come on when it shuts off.

Can anyone provide me some insight on what else might be going on so that I can have some good questions to ask the shop when I bring it back this Friday?

 

[OR VietVet]

Sounds like a failed/failing low pressure switch. Looks like this:https://www.rockauto.com/en/moreinfo.php?pk=436792&cc=1440055&jsn=916

Could be an intermittent problem with the compressor or clutch as well but that switch is way cheaper to replace if you are going to do the "parts guess swap" instead of diagnostics. Intermittent problems are the worst to try and diagnose.

Hell, it could even be a problem with the controller at the dash.

 

[Cbncanada]

Did you take it back for the dye leak check? They have a special light that shows the dyed leaks.

 

[A Ransom]

Sounds like a failed/failing low pressure switch. Looks like this:https://www.rockauto.com/en/moreinfo.php?pk=436792&cc=1440055&jsn=916

Could be an intermittent problem with the compressor or clutch as well but that switch is way cheaper to replace if you are going to do the "parts guess swap" instead of diagnostics. Intermittent problems are the worst to try and diagnose.

Hell, it could even be a problem with the controller at the dash.

Thank you,

I just found this video on YouTube

and will try this tomorrow.

I will let you know the results!

 

[A Ransom]

Did you take it back for the dye leak check? They have a special light that shows the dyed leaks.

I have my appointment this Friday for that.

 

[drakon543]

a leak is a possible problem. also both low or high pressure switches failing can be a problem as well. if you have borderline low freon it will have enough static pressure to allow the system to turn the compressor on. it may not have enough freon to build the required pressure to operate and trigger the pressure switches correctly and will then shut back off. if the one of the pressure switches is failing there's a potential for the system to get the same signals incorrectly and still shut off. 10 years without another failure is a good stretch as the only work you originally had done was a compressor replacement and a recharge. also 10 years on a compressor is a good chunk of time some compressors dont last that long. however the fact that it works at all on occasion im guessing its just a pressure switch or a leak.

 

[dnt1010]

Sounds like you have a rather large refrigerant leak from the information given. That may actually a good thing as they will be able to find it easily and hopefully in an easily repairable spot. Sounds like a pretty good AC shop if they did a replacement and it lasted 10 years.

 

[A Ransom]

Update.

I did what @PNW VietVet said and installed a new low A/C pressure switch and my compressor immediately came on.

I drove it for a couple of miles to get the engine heated up to see if the compressor would cut off and it did not.

My AC is blowing "ice cold" again. I still have my appointment for tomorrow to check for any freon leaks.

I'm wondering if I should have the other switched replaced just to get it out of the way.

Old switch



New one installed



Only cost $20 at Advanced Discount Auto Parts

Thank you once again @PNW VietVet

 

[OR VietVet]

I am glad that the switch took care of it.

There is an a/c compressor relay that is AC Delco part # 13500114 and looks like the one in this link: https://www.rockauto.com/en/moreinfo.php?pk=3779427&cc=1440055&jsn=930

I have heard but unsure about your year a/c compressor, about a high pressure cut off switch at the back of the a/c compressor but unsure if yours has it or not.

Besides the dash controller, that is about it for electrical choices for your a/c system.

Look at the back of your a/c compressor to see if it has that switch.

You may not have a leak afterall.

See, even this old man can call a shot every now and then.

 

[A Ransom]

I am glad that the switch took care of it.

There is an a/c compressor relay that is AC Delco part # 13500114 and looks like the one in this link: https://www.rockauto.com/en/moreinfo.php?pk=3779427&cc=1440055&jsn=930

I have heard but unsure about your year a/c compressor, about a high pressure cut off switch at the back of the a/c compressor but unsure if yours has it or not.

Besides the dash controller, that is about it for electrical choices for your a/c system.

Look at the back of your a/c compressor to see if it has that switch.

You may not have a leak afterall.

See, even this old man can call a shot every now and then.

I replaced the compressor relay in the fuse box this past Saturday thinking that might do the trick but it didn’t.

When I headed to work today the compressor came right on and the A/C blew cold air.

I’m thinking the problem has been fixed due to your suggestion.

I’m just surprised the repair shop didn’t check the low pressure switch initially since it was such a simple fix/solution.

I’ll find out tomorrow if there indeed was a leak or not.

I will check behind the compressor to see if there is a another switch.

 

[OR VietVet]

I replaced the compressor relay in the fuse box this past Saturday thinking that might do the trick but it didn’t.

When I headed to work today the compressor came right on and the A/C blew cold air.

I’m thinking the problem has been fixed due to your suggestion.

I’m just surprised the repair shop didn’t check the low pressure switch initially since it was such a simple fix/solution.

I’ll find out tomorrow if there indeed was a leak or not.

I will check behind the compressor to see if there is a another switch.

You have to remember that you had an "intermittent" problem. If it was acting normally and performing normally when in the shop and they were searching for a leak, then they could not find that. They could have done a WAG, wild ass guess, like I did and recommended the part and it did not fix it, then you would not have been happy. At this forum we have experience and want/need all the details you have and share with us. Right now, we both think it is fixed, but it could still not work right and go back to what it was doing. Then we are at square one again.

I can't see or test your rig from here. I can take my past experiences and suggest like I did. If I am right, I am a hero. If I am wrong, and you spent wasted money, I am not a hero. Just let the shop know what happened, share all details with them and go from there. Like @drakon543 and @dnt1010 said, get ready for a 10 year old compressor to also give you a problem down the road. It is an "eventual" happening. Hopefully there are no leaks found.

 

[A Ransom]

You have to remember that you had an "intermittent" problem. If it was acting normally and performing normally when in the shop and they were searching for a leak, then they could not find that. They could have done a WAG, wild ass guess, like I did and recommended the part and it did not fix it, then you would not have been happy. At this forum we have experience and want/need all the details you have and share with us. Right now, we both think it is fixed, but it could still not work right and go back to what it was doing. Then we are at square one again.

I can't see or test your rig from here. I can take my past experiences and suggest like I did. If I am right, I am a hero. If I am wrong, and you spent wasted money, I am not a hero. Just let the shop know what happened, share all details with them and go from there. Like @drakon543 and @dnt1010 said, get ready for a 10 year old compressor to also give you a problem down the road. It is an "eventual" happening. Hopefully there are no leaks found.

Since it’s been a little over 10 years since they replaced my old compressor, and I know they usually last 8-10 years, I’ve been waiting for that day to come.

Depending on what he quotes me this time I might just have them replace it next week when they put my new bumper on.

I will definitely let them know what I did this past week with the relay switch and low pressure switch.

 

[OR VietVet]

Usually a compressor will give you some notice before a failure. If you do open up the system, make sure you replace the accumulator and the orifice and I always recommend a complete flush of the system and make sure the flush flow thru the condenser is good before reassembly. If you do the compressor, typically their warranties dictate the accumulator replacement and a flush and I just do the orifice because. It is a cheap part. I used to tell my customers, at the shop I was at, that if the a/c system needed major work and it was close enough to fall weather and the a/c would hardly be used, that to wait till spring in case they have other problems that would need that money or God forbid, the rig gets in a wreck and the a/c fix money would be a waste. That system being that old should have a flush. Nothing helps a condenser work better than a good flow thru the inside and on the outside to help carry away that heat.

 

[A Ransom]

Just picked up the Kon and no leaks were found.

A/C low pressure switch was the issue all along.

 

[OR VietVet]

Now you have peace of mind. Good luck.