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1999 S-10 A/C cuts on and off at long term idle, and makes squealing noise.

My 1999 S-10 has 2 weird problems....

1: I take my work breaks in my truck. I will run the AC on hot and humid days. The air runs fine, then after a while, the compressor cuts off. It will cycle for a few minutes and then stay on. This does follow a pattern based on the vehicle's coolant temp guage. I *assume* this a way for the truck to "save itself" from an overheat condition befor the thermostat opens. Is this a correct assumption? The temp guage never goes higher than the halfway mark, and then drops a bit when I assume the 'stat opens. Just wanting verification of this odd behavior.... the vehicle is always at idle and never moves. AC functions perfectly when driving.

2: Any time the AC compressor/system cuts off, or is turned off, whether by the switch or by turning off the truck, there is a high-pitched squeal for a few seconds. This only happens when one of the AC settings is switched off. I do not believe this is normal, and indicates a vacuum leak. In the winter when using the heat, and following a similar situation, the noise is not heard. IF this is a sign of a problem, where can I look to correct it.

My vehicle is a 4 cyl 1999 S-10 w/ 4 speed trans.

Thanks guys!

Reply to
John L. Wilkerson Jr.
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This is normal.

Vacuum leak? Where the hell did you get that idea? Vacuum leaks make HISSING noises, not squeals. It's probably your belt squeaking when the extra load it put on the serpentine system. Replace the belt and/or tensioner. It could also be your A/C clutch is out of adjustment.

Doc

Reply to
"Doc"

"\"Doc\"" wrote in news:ddqdneKlnboLR0jdRVn snipped-for-privacy@adelphia.com:

It hisses also.... the "squeal" is kind of like when you squeeze air out of a baloon and stretch the neck tight so it makes that high pitched squeal. It definitely is NOT a belt. I think it is a vacuum leak when the system is disengaged.

Reply to
John L. Wilkerson Jr.

Does it make the noise every time the A/C clutch engages?

Doc

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Reply to
"Doc"

"\"Doc\"" wrote in news: snipped-for-privacy@adelphia.com:

No.... just when the AC is turned off, either by the switch, by turning off the vehicle, or when the AC clutch disengages. A hissing sound is followed by the squealing of air leaking through somewhere. I figure it is a vacuum control that is leaking

Reply to
John L. Wilkerson Jr.

He he he he. Here's what I think is happening. The A/C system will always hiss when the clutch compressor kicks off. This is the pressures equalizing between the high and low sides of the A/C system.

The squeal could be the clutch itself, or could be the serpentine system (yes, a belt squeal) when the excess load is lifted from the system. You need a partner to hang out in the cab and shut the A/C on and off until you pinpoint EXACTLY where the squeal is coming from.

Doc

Reply to
"Doc"

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