ac clutch does not engage

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91babyblue

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I got truck in garage around -10 or so with doors open. its a 1991 5.7 . while running I press the ac on inside the cab. all I see is ac blinking on and off. I am trying to engage the clutch. is it possible it is too cold to engage the clutch etc? I somewhat read it has to be a certain degree in temperature to run the ac. I'm just bought truck this winter. but want to see if air conditioner works. and also figuring out a possible squeak in the compressor area while idling.... When I bought it .the guy drove 3 hours away to my place , opened hood, there was no squeak then. probably warmed up fully. so it didn't squeak. I'm guessing. my main problem is I'm wondering about the squeak, and why the air conditioning clutch doesn't engage while engine is warm but cold outside??
 

Dariusz Salomon

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It should engage regardles. If clutch is not engaging probably something wrong in ac system. It may be empty or relay is not good or fuses-here's a lil video-you can jump the relay socket to check if your clutch is getting power at all.
Mind you yours is 91 so maybe the layout of the fuse box is different but the rule I think should be the same. That's one of the first things you can do to troubleshoot the ac system. Next you can jump the ac pressure switch. If you happy that electrically all works then you will have to check if your system is not empty. If it is-then you gotta chase the leak. I personally would add dye cause it's the easiest way to find where it leaks.
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1998_K1500_Sub

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I got truck in garage around -10 or so with doors open. its a 1991 5.7 . while running I press the ac on inside the cab.

At those temperatures (you mentioned "-10") the refrigerant pressure is so low that the pressure switch (on the suction side) won't close (which is proper) and thus the compressor clutch is not energized (which is the desired result).

Google a temperature / pressure chart for whatever refrigerant you've got in that vehicle and you'll see.

Here's a chart for R134a:

 

91babyblue

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At those temperatures (you mentioned "-10") the refrigerant pressure is so low that the pressure switch (on the suction side) won't close (which is proper) and thus the compressor clutch is not energized (which is the desired result).

Google a temperature / pressure chart for whatever refrigerant you've got in that vehicle and you'll see.

Here's a chart for R134a:

Oh thx for that I’ll book mark that. I thought I read something of that nature. Thx so much
 

1998_K1500_Sub

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I'm figuring out a possible squeak in the compressor area while idling....

A "squeak" or other noise in that area might be due to the tensioner or the bearings in any of the driven items (pulleys, AC, water pump, alternator, PS pump).

You can check if it's any of the above by simply taking the belt off the tensioner so it lies loose, and then start the engine to see if the noise disappears or remains. Do this quickly / stop the engine promptly as the water pump's not being driven when the belt's off.

With the belt loose, it's a convenient time to spin each pulley by hand and listen / fell for noise or roughness.

Speaking for myself, I replace idler pulley bearings fairly often, likely more often than necessary, because it's a stock off-the-shelf bearing that I happen to have in stock. Press the old bearing out, press the new bearing in, done; enjoy beverage.

I've replaced a perhaps three compressor pulley bearings... all on R4 compressors coincidentally.
 

highwaystar

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I'd first jump the pressure switch, if compressor comes on then it's low on freon. Add dye to find out why. Defrost work?
 

1998_K1500_Sub

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I'd first jump the pressure switch, if compressor comes on then it's low on freon. Add dye to find out why. Defrost work?

Not necessarily indicative of low charge. See my post.

That’s not good advice in general. In some specific situations, perhaps.
 
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