I used Classic Auto Air as well. But it was not an easy venture. I had to return it 3 times before they got it right. Problems ranged from complete failure and very loud operation to not clocking the clutch connector to the correct position. Of course they paid for all return shipping and rebuilding of my accumulator to finally fix the problem. I was on the phone with the techs for hours as they were trying to figure out what was going on. The manager eventually got involved.
In the end, they just swapped in another "gut pack" as they call it. Unfortunately, I burned through 3 recharges of R12 during this mess which was quite expensive. I also had to wait 6 months before they even initially got to working on my compressor and it was very expensive.
I think if I ever have to do this again (hopefully not!) I will buy a rebuilt outright.
I get emails from them since I'm on their mailing list. They sent one out where they were asking to buy old A6 compressors from anyone that might have them laying around. So they are apparently in desperate need of them.
