Air Conditioning Issue

[30579it]

Hey guys,

Having a strange issue with my 2001 Tahoe (rear AC equipped). I recently have replaced AC compressor, front lines, orifice tube, and dryer/accu. with OEM replacement parts. Put a vacuum on the system for an hour and had it recharged at a shop. AC blows very cold. 30-45 degrees on average even when OAT is 95-100 degrees. I have replaced fan clutch and also installed a pusher fan in front of the condenser for extra airflow.

On to the issue:

when the truck has been sitting in a hot parking lot for a few hours the compressor slugs at start up. It makes a pulsing noise and the air doesn’t get cold. I’ve put some gauges on it and pressures are high - 320psi or so (


what I usually do at this point is shut the AC sys. off and drive for 10-15 minutes before trying it again. This always “fixes” the issue - the compressor spins and cold air comes out of the vents. Once the compressor is going it blows cold even at idle. It was blowing 40 degree air when I was in a drive thru for 15 minutes yesterday in 100 degree OAT. No issues.

However, this slugging issue happens every time I start the truck after it has been sitting for several hours in the heat.

when I disassembled the AC system there were no signs of metallic flake in the orifice tube or any of the other parts. Everything looked brand new. I didn’t replace the condenser because it looked perfectly fine. No dings or bent fins.

I’ve been fighting this issue for the past few weeks. Any help would be greatly appreciated.

 

[OR VietVet]

Sounds like having valving problems in the compressor. You may have replaced all those components but I did not see you say anything about flushing the system before reassembly. That should have been done. What may have happened is crud in the system, likely hanging around in the condenser and evaporator, has now been freed up under pressure and roamed thru the system and damaged valving in the compressor. Hopefully I am wrong and there is an easier fix.

 

[30579it]

I was prepared to flush the system; however, I carefully inspected every line and component I replaced. Everything was spotless. The system had been running fine before I rebuilt it other than the original compressor had started to slug uncontrollably.
I figured the compressor had blown apart and sent debris through the entire system. But on very careful inspection, no debris was found. Even wiping parts with a white cloth found no sign of particulate.

If the compressor were damaged, it seems it would not work correctly regardless of OAT - just my opinion.

I wonder if I put too much oil into the system, and perhaps the high OAT increases condenser pressure forcing oil down into the compressor?
Any of that seem reasonable?

thanks again!

 

[OR VietVet]

Remember, I said the crud is likely hanging around in the condenser or evaporator or both even. I have done a lot of a/c work in my day, lived in hot humid KCMO. What you saw looked ok but what you can't see is what can cause a problem. In the a/c world, the crud that builds up in the condenser is nicknamed "Black Death". I never ever cared what old components looked like as I took them apart for a/c work. I was going to flush the rest of the system, no matter what. The other part of this story is that I did not ask, I should have, and you did not explain that the original problem was a "slugging" compressor and now we have a duplicate problem? Am I understanding that correctly? Is there a reason to hold that info back to begin with? Hell, at 68, I forget stuff all the time.

Again, I hope that it is something else.

 

[clandr1]

Is it possible that the prolonged exposure to heat causes ALL the compressor oil to run down into the compressor (which is the low point in the system) which causes a sort of hydro lock initially? If so, that might be an indication of too much oil in the system, but I'm grasping at straws based on my limited knowledge of the inner workings of the A/C system.

 

[OR VietVet]

I have seen too much oil cause problems and noises, so you could be on to something. Oil in a system can be tricky. If I ever had to open a system, in my shops, I always did the flush to remove old oil, replaced the orifice and accumulator and if replacing the compressor, make sure to note if the new compressor comes with or without oil in it during shipping. If I was reusing the old compressor I would dump the oil out of it. I would turn it for oil to come out and let it drip out for at least an hour while I did other things. I would then only add the prescribed amount of oil for the system.

 

[30579it]

Is it possible that the prolonged exposure to heat causes ALL the compressor oil to run down into the compressor (which is the low point in the system) which causes a sort of hydro lock initially? If so, that might be an indication of too much oil in the system, but I'm grasping at straws based on my limited knowledge of the inner workings of the A/C system.

I just logged back on and saw your comment. You are correct! I replaced the dryer and found an excess of oil in the one I had replaced a few months ago. I installed a new one. It’s blowing cold from start up now with no hydro locking.

 

[30579it]

I have seen too much oil cause problems and noises, so you could be on to something. Oil in a system can be tricky. If I ever had to open a system, in my shops, I always did the flush to remove old oil, replaced the orifice and accumulator and if replacing the compressor, make sure to note if the new compressor comes with or without oil in it during shipping. If I was reusing the old compressor I would dump the oil out of it. I would turn it for oil to come out and let it drip out for at least an hour while I did other things. I would then only add the prescribed amount of oil for the system.

Yes! That was my issue. I messed up and put probably several ounces too much oil. I had been told that “you can’t hurt a system with a little too much oil” or “if you put too much oil in the system, you would have blown up the compressor already - you need us to install a new condenser.”

thanks guys for the replies and help.

 

[clandr1]

I just logged back on and saw your comment. You are correct! I replaced the dryer and found an excess of oil in the one I had replaced a few months ago. I installed a new one. It’s blowing cold from start up now with no hydro locking.

That's great! Glad you figured it out, and thanks for coming back and updating the thread.