Started last year. When I started up my truck I would hear a loud squeal for a second or two and then another loud squeal when I turned on the A/C. Took it to the shop and they said it was A/C compressor internal failure. $1800 to replace. I said no.
Fast forward to Summer 2021 and it's starting to do it again. One thing I noticed is that it only seems to do this when it's sunny and hot out. Today is a cooler day and when I started up the truck no squeal. Any ideas? Could it be belt tensioner?

 

On hot days your A/C is engaged upon startup and on the cooler days it's not?

 

I'm partially in the same boat, but I've yet to actually get it properly diagnosed. My squeal is typically just a quick chirp or two right after startup, when the A/C engages. It also only seems to happen if the engine isn't warm. Well, warmer than just sitting outside in the sun anyways.

 

It's not engaged on startup for either scenario.

 

Could be any of the following:

1. Glazed belt (try a little spay belt dressing).
2. Idler pulley bearing (wait until it gets worse to properly diagnose).
3. Weak tensioner (unlikely at this age).

 

Yep, had all three at one time or another including an alternator bearing.

 

Don't think it could be the A/C compressor internal failure?

 

No. If that is what was causing the problem a year ago, it would have failed long ago.

What engine do you have?

 

A compressor squealing for a second or two on startup does not guarantee a failure within any specific timeframe. It could still be a bad compressor shaft bearing or seal, or hopefully something cheaper.

A squeal that occurs on startup and also when engaging the compressor is not going to be an idler. Your options are a belt slipping under load when the compressor clutch engages, the compressor clutch slipping during engagement, or a compressor shaft bearing or seal.

Could also be TWO noises, a squeal on startup that is affected by temperature (like an idler), and another that is in the chain of three I mentioned above.

 

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