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A/C compressor squealing


FatMike86

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First the vehicle: 89 Ranger 2.9L automatic; FS6 compressor w/134A conversion done about 3 years ago

So I recently had this awful squealing sound coming from the compressor, it sounded like a dinosaur was barreling down the highway. Not the belt, but the compressor was actually not spinning. Noticed it only happens when really hot out (like 100+ degrees). After trying a few cheap fixes I decided to just do an overhaul of the system using MAKG's AWESOME a/c write-up. Flushed the system, replaced the compressor, orifice tube and dryer with new units. Re-oiled and filled with R134A, and everything was working great. Then the other day it reached 102 degrees and I noticed it started again, so I immediately turned off the a/c. It hasn't done it since, but I noticed the compressor does have a little bit of a squeak when it's on.

Anyone have any ideas? I mean everything is brand new, besides the condenser, evaporator, and all the lines...maybe I didn't add enough oil? I put 4ozs of ester oil in the compressor and 4oz in the dryer, just like the write up said to do...
 


MAKG

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Oh boy. It's probably not good news.

FIRST, try to turn the compressor hub by hand, with the engine fully warmed and off. If you can, that's good news; check your belt tension (it's probably loose) and replace the drivebelt if the tension is good.

If you can't turn the hub with your hands, the compressor is bad. Recover the refrigerant and pull the orifice tube.

Three things can cause rapid compressor failure:

1. Contaminants in the system, especially grit from the previous failure (though some folks claim otherwise, I just don't see how one can authoritatively flush a condenser). Water contamination can do this, too.

2. Overtightening the drivebelt (on non-serpentine systems).

3. Overcharging. 80% of R-12 capacity by weight, from 29 inches of vacuum. Usually around 2 full cans of R-134a.

In any case, the orifice tube will give you hints as to what failed.
 
Evan

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MAKG said:
I just don't see how one can authoritatively flush a condenser).
Click to expand...

It's easy, just run water through it for 10,000 years.

Most RBV AC compressors have 6 cylinders with 3 symetric pistons driven by a sinusoidal cam in the center. The assembly is controlled by check valves on each end. If the cam becomes scored in any way, the compressor fails quickly. There is also a front and rear sector shaft bearing, as well as a pulley bearing that can sieze and fail.

I once took apart a siezed compressor and attempted to "rebuild" it. I polished the scoring out of the cam and reassembled it. It worked great and I was quite proud of myself, until it siezed three minutes later....so violently that it killed the engine.
 

FatMike86

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Thanks guys for the ideas. I spun the compressor hub by hand; spins just fine with no noise or slop. I do think I might have the belt a little too tight; when i push it between the compressor and the crankshaft it moves about an inch, and about a half-inch between the compressor and the camshaft. I think I'll go get a fresh belt and loosen it up a bit. As far as the amount of refrigerant, I'm not sure how much I added because I added it from a big tank of 134a. The system is reading about 37 psi. Could that be too much pressure for the compressor?

The air is blowing cold and the compressor is spinning, it just has a little squeaking noise; like a shopping cart wheel that needs some WD40. That was where I was thinking it might need some more oil...

I'm obviously a shadetree mechanic that learns as he goes; so I do appreciate your help.
 
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MAKG

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If the belt is slipping, it's LOOSE, not tight.

It might be a good idea to pick up a belt tension gauge and do it right. A tight belt is FAR worse than a loose one.
 
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