Swapping A/C Compressors

Almost a year after converting my r12 system to r134a, the compressor gave out. I got a hold of a used r134a compressor out of a 94 XJ, and I was going to do a swap. What different A/C components do I need to replace when I open the system up? Can I charge up the system myself with cans of refridgerant or do I need to have a vaccum on it? It was about 94 degrees down here in MS today so I am anxious to get this done. TIA.

The reason for the failure is simple - apparently, head operating pressures for R134a are somewhat higher than those for R12, and that will lead to premature compressor seal failure.

If you've already done the conversion from R12 to R134a (including switching out the receiver/drier and associated componentry,) you should just need to change the compressor. It will be necessary to draw the system to a vacuum before charging, but if you have a big enough air compressor, you can get a vacuum pump for about $40-50 and do that part yourself. If you have a manifold gage set (they are different for R12 and R134a) already, you're probably going to come out ahead if you get the vacuum pump. If you don't, it will probably be cheaper to get the system done at a shop rather than buy the gages/pump/coolant/&c.

Don't forget lubricating oil - it's usually a good idea to "manually" oil the compressor before installation. Pour about a teaspoonful of oil into the suction port, and turn the compressor by hand. As the suction port dries out, add more oil in small quantities until you start seeing oil come out the discharge port. This will ensure that the compressor is already lubricated, and that you won't end up running it dry and setting up for premature working seal failure (and doing this job again next month.)

5-90

Just went through all of this. I had a squeak that seemed to be coming from my old compressor so I had a shop install a reman one and convert from 12 to 134a. We didn't change anything else because the old compressor was working well other wise.

The compressor failed in a week. While the reason for the failure is unclear, when it went it blew enough stuff into the system that it plugged the condenser so bad it wouldn't flush out.

It took some talking to get the compressor warranted. Most warranties are contingent on the filter/drier being changed out at the compressor swap.

If your old compressor failed during operation I would strongly suggest swapping the filter drier and having the complete system flushed.

Condensers are damn expensive and usually the lines have become one with the condenser as well. I ended up replacing the compressor, orifice block, all lines, the filter drier, and the condenser today. :repair:

Don't know if it would have been avoidable if I had swapped the filter drier with the first compressor, or if it was just a bad compressor, but it couldn't have hurt.

Bones :skull1:

You shouldn't have any more trouble... you took care of all of the components.


Did you check the condenser for blockage with compressed air before putting it all back together?


JC95

Alright, I removed the old compressor and replaced the receiver/dryer but I have a problem. The old compressor had the valves attached to the back and the compressor I have that was out of a 94 has different size connections. Am I going to have to have the a/c lines out of a 94 to use this compressor?

The new compressor has R134a style fittings. The old lines still have the R12 style fittings. Autopart stores should have the adaptors for a couple bucks, we sell a ton of them at NAPA but I forget the part numbers just ask for the R-12 line, R134a compressor adaptors for the high and low side.

You will need to have some place like Napa make you new lines. You really need to get the debris from the failed compressor flushed out on the system too.

What's the best way to flush out the debris?

DannyXJ said:

What's the best way to flush out the debris?

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I only know of a machine that's made for that purpose, it's not a DIY thing.

Does anyone know if the a/c lines out of a newer XJ with r-134a have the same size fittings as a 91 with r-12? I was going to try and run by a salvage yard to pick some up if they will swap right into my jeep.

DannyXJ said:

Does anyone know if the a/c lines out of a newer XJ with r-134a have the same size fittings as a 91 with r-12? I was going to try and run by a salvage yard to pick some up if they will swap right into my jeep.

Click to expand...

NO. R12 Lines and 134 are NOT compatable. Fittings are different.

I have a 94 compressor....Are the fittings to the condenser and the expansion valve also different?

DannyXJ said:

I have a 94 compressor....Are the fittings to the condenser and the expansion valve also different?

Click to expand...

Different than what?

I'm sorry....different than a 91 XJ r-12 system

DannyXJ said:

I'm sorry....different than a 91 XJ r-12 system

Click to expand...

All the fittings are different as are the hoses, r134 don't work as well either.
Stick with the r12 system and recharge with freeze12 and it will work better than new.