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re:Testing ac compressor.

yorled on Thu June 03, 2010 11:37 PM User is offline

I am replying to an article in the flushing forum and I quote,"there are bench tests involving dead-ending the high side,and measuring the pressure."Explain exactly what this means,especially "dead-ending"the high side.

NickD on Fri June 04, 2010 10:20 AM User is offline

With reading the article, just some things you can do to be half assured that compressor is workable before installing it in a vehicle to learn it either leaks, or cannot provide its pumping function, these are age old tests. First is to and turn the compressor to be assured of no rough spots and smooth operation.

One is to charge it with 100+ psi of air, requires jury rigging the outlet plugged with the air source jury rigged to the inlet, dropping the compressor into a container of water and checking for air bubble leaks very similar to checking an inner tube.

For function to jury rig a vacuum gauge such as a low side gauge to the inlet and a pressure gauge to the outlet and hand turning the compressor. With most compressor can get close to 30"/Hg at the inlet and maybe up to a 100 psi at the outlet just by hand turning it the same direction it turns when connected to the engine, typically clockwise. When stopped turning, those gauge indications should hold for at least a minute, reed valves are not perfect sealers, but the pressures should not drop instantly, the gauges should slowly return to zero.

Jury rigging is the major problem, have to go to a wrecking yard to obtain the appropriate fittings and somehow find hoses, clamps, gauges for an air tight seal. Also concern about the clutch coil, idler pulley bearing and overall condition of the clutch. Certainly not worth the effort if you found a compressor laying in a mud puddle. Impossible if not impractical to find replacement parts for these things. Also depends upon if you have a lot more time than money, but still the uncertainty of how long this old compressor will last. In recent years, just the act of charging and recovering makes this once an easy inexpensive procedure that can be all wasted time in dealing with an old compressor.

For the price of just a clutch kit, a few bucks more will buy you the compressor with the new clutch already installed. Run into this with other things, had a bad master cylinder and have the honing equipment, parts store wanted just as much for the rubber kit as a new master cylinder. 98% of the time you can clean half axles regrease, and put on new boots and they will be like new again. But my parts store wanted more of a pair of new boots then the price of a rebuilt half axle with new boots already installed. So why should I go through all that extra work? Same with compressors.

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