A/C blows warm air after idling a few minutes

2000 GMC SIERRA
263,000 MILES • 5.3L • V8 • 2WD • AUTOMATIC
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PACKERS27
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So the A/C is cold like it should be but after a few minutes at idle, the cold air leaves and it's just warm air. Under the hood, I can a constant rattle, and it rarely goes away. Is the A/C clutch staying on? I've tried to Freon it up but if the rattle is actually the compressor stating on then it doesn't go away, as if it's low of Freon. So now I'm thinking it's something with the A/C compressor but a lot of people are saying it's the radiator fan clutch. Thoughts?
May 27, 2021 at 9:16 AM
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ASEMASTER6371
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Good afternoon,

Does the clutch stay engaged when it blows warm air?

I would get a set of gauges and check the high and low side pressures to see if it is overcharged. If it is, it will knock.

https://www.2carpros.com/articles/re-charge-an-air-conditioner-system

Can you upload a video of the noise? It very well may be the compressor. Disconnect the wire to the compressor and see if the noise goes away.

https://www.2carpros.com/articles/replace-air-conditioner-compressor

Roy
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May 27, 2021 at 10:51 AM
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PACKERS27
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I don't think the clutch stays engaged when it's not blowing cold air. Isn't the radiator fan clutch a common issue to this problem?

I wouldn't describe the noise as a knock. It's hard to explain but it's not loud. The compressor stays on a long time and I can't get an accurate reading because of it.
May 27, 2021 at 9:32 PM
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ASEMASTER6371
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Okay, I need those pressure readings when the engine is running. If the compressor is off, then there is something wrong with the pressures.

The fan clutch pulls cool air through the condenser for cooling down the condenser. If it is bad, it would reflect it in the pressures. The high side would be very high from lack of airflow.

https://www.2carpros.com/articles/fan-clutch-symptoms

https://www.2carpros.com/articles/fan-clutch-removal

You can get a cheap set of gauges at Harbor Freight and then do the test.

Roy
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May 28, 2021 at 1:59 AM
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PACKERS27
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Okay, I will get some gauges from Harbor Freight. Until then, here's a video of the sound.
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May 31, 2021 at 2:28 PM
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ASEMASTER6371
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Thank you.

You need a compressor. I would replace it and evacuate and charge the system.

https://www.2carpros.com/articles/re-charge-an-air-conditioner-system

https://www.2carpros.com/articles/replace-air-conditioner-compressor

Roy
May 31, 2021 at 4:01 PM
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PACKERS27
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Thank you.
Jun 2, 2021 at 8:01 PM
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ASEMASTER6371
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You are welcome.

Always glad to help.

Roy
Jun 3, 2021 at 2:39 AM