93 silverado a/c stops at low rpms

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  #1  
Old 07-20-06, 12:33 AM
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93 silverado a/c stops at low rpms

Hopefully someone here can give me some clues where to look. My a/c works great when I first start the truck, it will run cool for awhile, then after say 15 min if my rpms are lower than 1500, the compressor will shut off. I pull the plug on the side of the accumulator and shorted it, which I heard was suppose to make the compressor turn on.

I picked up a cheap gauge to test the pressure... it looks like a tire pressure gauge, it says the low side is at 42 psi, so it's full. The temperature gets down to 50 in the vent, so the compressor is working good. It sounds like there is some sort of switch that is shutting it off during lower rpms.

Thanks for the help

I edited these posts as I was testing the plug on the accumulator, not the condenser.
 

Last edited by kuyote; 07-20-06 at 12:04 PM.
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  #2  
Old 07-20-06, 03:45 AM
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Originally Posted by kuyote
Hopefully someone here can give me some clues where to look. My a/c works great when I first start the truck, it will run cool for awhile, then after say 15 min if my rpms are lower than 1500, the compressor will shut off. I pull the plug on the side of the condenser and shorted it, which I heard was suppose to make the compressor turn on.

I picked up a cheap gauge to test the pressure... it looks like a tire pressure gauge, it says the low side is at 42 psi, so it's full. The temperature gets down to 50 in the vent, so the compressor is working good. It sounds like there is some sort of switch that is shutting it off during lower rpms.

Thanks for the help
kuyote,
I think I know what your problem might be but the moderators on this site keep deleting A/C information. Something about a legal issue if someone does something illegal that they read about here??????

Hopefully this won't get deleted!
The pressure guage you have is junk. Throw it in the garbage now. (or sooner) It doesn't tell you if your system is full.
Good luck,
Phil

If you want answers to your Auto A/C questions (without them getting deleted go here:
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Or here:
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Last edited by mattison; 07-20-06 at 03:51 AM. Reason: Links to outside forums not allowed.
  #3  
Old 07-20-06, 03:53 AM
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Originally Posted by kuyote
Hopefully someone here can give me some clues where to look. My a/c works great when I first start the truck, it will run cool for awhile, then after say 15 min if my rpms are lower than 1500, the compressor will shut off. I pull the plug on the side of the condenser and shorted it, which I heard was suppose to make the compressor turn on.

I picked up a cheap gauge to test the pressure... it looks like a tire pressure gauge, it says the low side is at 42 psi, so it's full. The temperature gets down to 50 in the vent, so the compressor is working good. It sounds like there is some sort of switch that is shutting it off during lower rpms.

Thanks for the help
kuyote,
Sorry buddy, you're on your own!
The moderators deleted the threads I listed.
Good luck,
Phil
 
  #4  
Old 07-20-06, 03:54 AM
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We don't edit a/c info period, just refrigeration side advice.

Have you tried cleaning your condensor? you may want to get the pressures checked by a shop to be sure the pressure isn't dropping low enough to cut it out on low pressure.
 
  #5  
Old 07-20-06, 12:00 PM
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If my pressure sensor was bad, wouldn't I be able to tell when I jumped the plug coming out of the accumulator? I thought this would kick the compressor on?
 
  #6  
Old 07-20-06, 12:15 PM
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You are correct but he A/C must be turned on the dash first.
 
  #7  
Old 07-20-06, 12:52 PM
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probably should have the pressures checked with manifold guages if it only kicks off when your idling or moving slow could not be getting enough airflow through the condensor, unsure if you have a high pressure cutout switch on your model it is usually on the back of the compressor if it has one it will kick out the compressor if high side pressure is to high, you could try running some water over the condensor to see if the compressor stays engaged if it does better check the fan clutch.
 
  #8  
Old 07-21-06, 06:53 PM
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I went out and ran the a/c for awhile at idle, with a hose running over the condenser, and it never seemed to stop working, I also noticed some of the fins of the condenser were smashed which could lead to some of cooling problems. My next step should I replace the fan clutch and see if that solves it? I am assuming the condenser isn't damaged too bad, since it reads about 50 degrees.
 
  #9  
Old 07-21-06, 07:33 PM
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a good test to check air flow is to place a shop towel or rag up against condensor with engine idling it should have enough flow to hold it there if it trys to fall would suspect the fan clutch.
if the system has been worked on recently or charged it is possible that it could be overcharged causing the pressure to be to high.
the condensor fins can be bent or damaged a little if its over a large area it could be contributing to the problem also.
 
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