General AC question

[Jesda]

Last year I had a remanned compressor installed in the Saab with r134a. It replaced the original compressor which I had charged with R12, ran GREAT for a few days, then seized.

After a few months the remanned unit started to seize up occasionally. Thinking it may have been due to excess refrigerant I removed some refrigerant which reduced the occasional seizing but caused it to of course cool less effectively. I then disconnected the electrical connection to the compressor and have been driving without AC since last year.


Should a new compressor do the trick or do you think something else is going on?

[driverdriver]

Maybe there is a leak caused from excess refrigerant that burnt out the compressor? Have you done a "leak down" test with one of those kits you can find at auto parts stores?

[NolimitZ32]

Have you pulled vacuum, are there any other symptoms? Most likely being that its a fairly old car, the o rings & other seals in the old compressor had started to disintegrate and chunks of these are in your lines, when these chunks get into your new compressor they will slowly start to build up on the internal moving parts which leads to the problem you describe. All this is affectionately called by some "Black Death" only way to remedy is to fully flush the system, get a new expansion valve & very likely new compressor. there is really no way to tell if you have the black death short of pulling the lines off the compressor and running compressed air through them.

[IanS]

Hmmm

Define seizing. Does it not spin up when the clutch engages, causing the belt to squeal, or is it stopping durring normal operation, and causing the belt to squeal.

Have you checked the belt tension? Older systems tend to be picky about belt tension, they want a very tight belt.

Excess refrigerant can cause lock up due to liquid entering the low side port, though it takes a pretty heavy overcharge to cause this.

It could be that the compressor is oil slugging. The new compressor was likely filled with oil when it was installed, and if the system had been charged a few times prior, each time with oil being added, you could have an excess amount of oil in the system. The easiest way to fix this, is to replace the receiver/dryer, and fully evacuate the system. This should clear excess moisture and oil from the system.

The other issue, may have been contamination in the system. When the prior compressor failed, its possible that it dumped shavings into the systems, which then killed the new compressor.