A/C Noisy..........Really Noisy!

I have a 87 chevy fleetside pickup, powered by a 4.3L V6 TBI,  It runs and Idles fine, The minute I turn on the A/C I get this horrible Groaning vibration through the fire wall,  looked under the hood, all mounting and support brackets are in place and the engine is rattling like crazy,  turn off the A/C, the noise stops and the engine smooths out.  There is no vibration or noise while driving at a constant pace on the freeway or around town with the A/C on,  but in stop and go traffic, waiting at light/sign, or coasting the moaning vibration returns.  The A/C blows extremly cold, and I assume still has the old R12 refrigerant (no retro connectors).  I thought about adding some R12 (if I can find some), but that would cost more than a retrofit.  I am getting ready for an Engine swap to a stroked 350 with a newer style serpentine dive and A/C compressor, but I looking for a quick/cheap fix for my current problem until the budget is right to follow through with the engine swap.    ANY IDEAS GUYS??????  

just curious....     does the belt flop a lot ???? is it tight enough... is the compressor starting to seize..  

nope,  belt is tight, I thought the compressor was seizing first time I turned it on (only had the truck for 2 years)  but it clears up when the engine gets some RPM.  Just at an idle or coasting!!!  

got a broom stick??????    take one end and touch it to something on the motor...  the other end to the area in front of your ear...

care is needed... so you don't touch anything moving...   only things that are solid and have moving things attached to them...

you will be able to hear the various noises the various parts make...  isolating them...

again care is needed... so you don't get it into anything moving...  touch the alternator case...  the AC case... the power steering case...  perhaps the top of the water pump....   the blower motor housing...  the belt tensioner arm...

with the engine off.. grab the front disc on the compressor pulley... see if it rotates smoothly.  there will be pressure when you turn it.. but you can tell the difference between a working ac compressor and one that is about to seize up...

i have also had to change several compressor clutch bearings.... not something for the learners.. it takes several specialized tools.. some are rentable.. but not all  stores have the right ones for your system...


you describe the noise ... is it coming from the blower. or the engine area...  

A broom stick huh?  Havent tried that particular approach yet, but I guess its worth a shot.  Well, Im a mechanic by trade, and Im A/C certified, Ive heard Compressors before they lock up and usually you get some kind of belt squeal while its running,  this has no belt squeal what so ever.  I really think the noise is caused by vibration.  The amount of load put on the engine (4.3L mind you) is so great that the whole engine compartment shutters with a loud groaning sound.  Its defenatly coming from the A/C compressor, the whole engine shakes when the A/C clutch is engauged.  I would probably change the whole compressor and retrofit the system before I tore into the clutch drive.  

Could be a problem with the clutch locking up too hard.

I'd try swapping in a new compressor/clutch combo and see what happens.  

does the a/c still work good? I put a new (pancake) style compressor on a truck and it rattled terrible but it worked great. The clutch was the noise, the customer didnt like the noise so I had to replace the compressor. just a thought.