92 Roadmaster AC Compressor Differences

[rdmaster92]

The AC Compressor on my 92 Roadmaster Estate Wagon just seized up on me. I had converted to R134a 7 years ago, and the AC worked well until Friday. Then Saturday there was no cold air coming out, and I found the clutch was not engaging the compressor, and was emitting a burned smell.

I went to the salvage yard to find a replacement, and was told that 91-93 Roadmaster with O-ring on the suction port, as well as 91-93 Caprice should work. I found one on a 91 or 92 Roadmaster Sedan (mfg date 06/1991), and purchased it. However, when I compared the two, I found that the one on my car has an additional electrical connector on the back of it, in addition to the connector on the front for the AC clutch. The compressor I purchased does not have the second connector. At the very least, I need to use the replacement as an idler pulley, as the pulley on the existing compressor is very loose, rattling and scraping badly.

Can anyone explain to me what the extra connector is used for? I have the Automatic Air Conditioning option, C68, and I assume the difference has something to do with that. If I install the replacement compressor and charge it, will the system still work? Or will I experience problems, like no AC, or the AC control head's computer shutting down?

Thanks in advance for any advice.

[HotZ28]

The extra wire on the back of the compressor is for the “high pressure” shutdown switch. If for some reason, the compressor should reach the maximum pressure allowed by the high pressure switch, the switch would disengage the clutch to prevent damage to the system components.


Now, if you are the lucky sort of guy, you may never need the high pressure switch, however, if your luck runs out, or the orifice screen gets clogged, the high side pressure may rise to unacceptable limits. If this ever happens, it could damage the condenser, evaporator, compressor, accumulator, or hoses. It is a gamble to run for extended periods without a “high pressure” switch. Good Luck, if you decided to go that route!

[rdmaster92]

Thank you. This is excellent information and exactly what I needed. The car has 210,000 miles on it, so I don't figure on worrying about too much of the future. I figure that I'll just recharge it with R134a and run it. I already have the replacement compressor in place, end will replace O-rings before I charge the system.

I also read a recommendation in my service manual to put in an aftermarket liquid line filter and oriface (expansion tube). It also says to remove the original expansion tube when I put in the filter and oriface. The manual does give the location of the expansion tube. Any idea on how hard it is to get it out, especially lacking tool J 26549-E?

'92 Roadmaster Est Wagon
5.7L with 4L60
210K miles
C68 option Automatic Air Conditioning

[HotZ28]

Originally Posted by rdmaster92

Any idea on how hard it is to get it out, especially lacking tool J 26549-E?

A good pair of needle nose pliers will suffice.