A/C blows warm air after idling a few minutes

PACKERS27

MEMBER
2000 GMC SIERRA
5.3L
V8
2WD
AUTOMATIC
263,000 MILES

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?

7 Replies

ASEMASTER6371

MECHANIC
52,797 POSTS

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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Thursday, May 27th, 2021 AT 10:51 AM

PACKERS27

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187 POSTS

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.

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Thursday, May 27th, 2021 AT 9:32 PM

ASEMASTER6371

MECHANIC
52,797 POSTS

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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