Keywords: compressorworks compressor works R4 air conditioning rear seal W123 1983 300CD 300D 300TD Delco Harrison GM
I’m re-habbing my air conditioning and replacing the compressor. This should be an easy job: one belt, six bolts, available parts. But no……
Warning/disclaimer: Venting or discharging your refrigerant (R12 or R-134a) into the atmosphere is illegal (and messy, and dangerous). Get your system evacuated, then work on it.
Wear goggles – there’s no end of greasy crud under your car.
Try to wear gloves – I did sometimes, but the darn Texas summer heat made that more miserable than greasy dirty hands
I’m removing a Harrison HR100T compressor and replacing it with a CompressorWorks 620230 unit. Both are R4, neither are M-B OEM.
I’ll skip the diagnostics that led me to decide to replace it. (highlights: leak from rear seal, probably bad clutch bearing, possible bad front shaft seal and maybe bearing, already evac’d system once…)
Get your parts:

Compressor – bought from a major chain for less than $200. CompressorWorks R4 compressors are made in Dallas and are reputed to be the source for re-branded units for Delco and others. That’s rumor I read on the Internet, but if you’re price shopping, you may want to ask the source before paying extra . http://www.compressorworks.com/

Belts – I went ahead and got all four: 2 x alternator belts, P/S belt, compressor belt. You don’t HAVE to replace the belt, but mine were old from the PO, had some wear and cracks and I figured I’m halfway there with the P/S pump and A/C belt out, so I’ll do ‘em all. It’s probably a good idea to buy alternator belts in pairs, from the same production run. That way they’re no-kidding the same size.

Oil – This is not a trivial decision. Are you going R12, R-134a, or just not sure? If R12, get mineral oil, if 134a, go for a 150 viscosity double end capped PAG, if you’re not sure go with Ester. I’m going 134a, so I used DEC PAG. What is “double end capped”? I don’t know, since I’m not a petro-chemical engineer but it refers to the oil molecule and it is resistant to absorbing moisture. See here for a science experiment with test tubes, graduated cylinders, and words like “polymerize”: http://www.autoacforum.com/messageview.cfm?catid=20&threadid=17571

Seals – this was the bane of the install. More later, but look here to see the rainbow of variety of sealing washers for GM compressors. For this specific install I needed the yellow one and the green one. Of course, I didn’t have them or know that. The major chain compressor did not come with them. The pic for the compressor at the AllParts site shows them, too. Do not assume you can re-use your old ones. http://autoacrepairs.com/sealing_washers.htm

Receiver/dryer – I won’t cover it in this install, but if you’re opening up the system you may as well replace this. They’re listed for some astronomical price, but you can buy Behr brand for less than $20 online.

Get your tools, at a minimum:

Phillips screw driver, 19 mm socket and wrench, 15 mm, 13 mm,10 mm, various adapters and extensions and drives. One of the most useful combos I found was using 1/4 inch drive hinged ratchet with a 3/8 adapter and the 19 mm socket. It made for faster turning after the bolts were loose. I also got the loaner clutch wrench from AutoZone.