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Dutchess_III's avatar

What does the AC compressor in a truck do?

Asked by Dutchess_III (43344points) April 19th, 2011

Most importantly, is it critical? We gave my daughter a 95 Suburban. It hasn’t had AC for the last two year, no big deal. Recently it started making some noise. She had a couple of home grown mechanics look at it. They said it was her AC compressor. However, they said, it runs more than the AC. It cools the whole engine down, or something. One told her it could catch on fire if she left the truck idling, the other told her the truck could flat lock up on her at any moment.

Needless to say, she parked it immediately while we try to figure out how to get a part (how to afford it is the main thing) and find someone to install it.

Can any of you give me any further info? It’s a 95 GMC Suburban 1500, 7.5 liter , 4WD.

If we can find a decent used compressor, what should we expect to pay for installation?

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8 Answers

john65pennington's avatar

AC compressors are very expensive. Here is a hint: Go to AutoZone or a related store and talk to one of the workers there. They can give you the price of an AC compressor for your truck. Most of the employees at auto parts stores are mechanics on the side. Ask around if they know of anyone that could install the compressor for you. My radiator went out in the dead of summer heat. I bought the radiator at AutoZone and one of the workers installed it in my car, after hours, for $50 bucks. Not bad.

The compressor for that truck is big and expensive, so you can expect sticker shock. Be prepared for it.

Dutchess_III's avatar

Well…she thought she had a bead on a used one for $50 but that fell through. New was $250. What does the AC compressor DO?

Thanks for the hint though John. It seems that auto mechanic garages are becoming a thing of the past….

jaytkay's avatar

Air Conditioning compressor.

When a fluid expands, it gets cold. You may notice this when spraying from an aerosol can.

Air conditioners (and refrigerators) work by letting a fluid expand and cool its surroundings. After which it needs compressing again. Repeat.

How Air Conditioners Work

Dutchess_III's avatar

@jaytkay I got that part (my husband sells commercial air compressors for a living!)...but is it just for the actual air conditioning, which we can live without, or does it cool the entire engine, which we can’t?

Thanks for the answer~

jaytkay's avatar

The radiator cools the engine, the AC does not. However there can be an problem if the belt which turns the compressor can’t turn, because it may also run the alternator which is essential.

Some answers in this thread from another site describe the situation.

Also, your defroster may use the AC to dry the air, so it won’t defrost as well without AC. Not a big deal, and maybe none at all in your climate.

Axemusica's avatar

The AC compressor does nothing more than provide you with Air Conditioning. Unless the clutch on the actual compressor is locked on, (The clutch is what triggers the compressor to turn. Ever notice when you’re using AC and you’re standing next to the vehicle and you hear wind & intermittent clicking? That’s the compressor turning on and off, e.g. providing cool air.) there’s nothing to worry about. Yes, the freon in the system is hazardous to your health and is known to cause cancer in the state of California, like everything else is, lol, but if it’s already drained out, which if you don’t have AC I’m assuming it already is there’s nothing to really worry about.

Here’s worst case scenario, if the compressor is locked up it can cause you to break the belt. This will cause the engine from running altogether. If anyone you know is familiar with mechanics have them do this for you. Release the tension on the belt going to the compressor and try rotating the compressors pulley. If the pulley moves freely, there shouldn’t be anything to worry about. If it does not, you’ll have to put in a bypass system (this being a shorter belt eliminating the compressor from the system with still operating other vital parts that run off of the belt line or I do believe they make pulleys that do nothing more than finish the belt system by placing it inline where the compressor used to be.) & depending on the options based on your particular model would lead you to the correct replacement.

The compressor doesn’t cool the engine. The cooling system does, e.g. hoses, radiator, water pump, ect..
Also, unless the pulley on the compressor is really screwed up I highly doubt it will catch fire either. Fires under the hood are usually only cause by electrical problems and or fuel delivery problems. I doubt the compressor turning on draws that much power to cause an electrical fire, but I’m no electrician.

Dutchess_III's avatar

@jaytkay Fantastic! Thanks so much! That’s what was throwing me….here in Kansas, where the extremes can run from -20f to 115f…meh. Who need AC?! Plus, it quit blowing cold air at least two years ago. (As far as the defrost…I drove a van for two years that not only didn’t have AC, it didn’t have heat! To defrost the windows in the winter meant starting the van an hour early)

Good news….she got the part, used, and installed, for only $60. Now I’m wondering if he didn’t buy a part but removed ”...the clip behind the a/c pully so that the a/c clutch cannot engage, you should be good to go with no a/c but no problems to the rest of the engine operation.” But, whatever. She has her vehicle back.

Thanks for everything….Ah @Axemusica…thank you. Hail, I could have trouble shot that myself.

Thanks everyone. Check’s in the mail.



john65pennington's avatar

Dutchess III, you are welcome.

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