By Glenn Goodspeed (August, 1998)
The Volvo ran out of Freon (Refrigerant 12) in the middle of one of the hottest summers on record, and I had none left to replace it. I knew exactly what to do, having researched the new refrigerants and "retrofit" procedure required to replace the obsolete R-12 with R-134a.
I opened my J.C. Whitney catalog and ordered service port adapters, a can tap and a gauge set. This was the first of several small errors that turned the conversion into more of a project than a procedure. When the things arrived from J.C. Whitney, I found flimsy aluminum port adapters with a rinky-dink little pin in the middle of each that was supposed to act as an extension to the existing Schrader valve pin in the original port. The gauge set looked o.k., but the hoses that came with it were as bad as the port adapters. Some had aluminum fittings, some brass, and they looked cheaply made. One of the service port quick-connect fittings did not work.
Fortunately, I had seen better-quality items at Pep Boys (alas, at higher prices), so I sent the junk back to Whitney and paid the price for decent equipment. The adapters are steel, and they include complete Schrader valves, so you remove the old ones before fitting the adapters. The gauge set costs three times what an old R-12 set costs, and the increase seems due mostly to ridiculously overzealous attempts to keep tiny amounts of waste refrigerant out of the atmosphere.
Both the Whitney gauges and the Pep Boys model came with a device specifically designed to defeat the stupidest of these precautions, a Schrader valve in the end of the charging/vacuum hose. I won't go into more particulars. Just be prepared to do some instant engineering if you buy new gauges.
I went to a local auto supply (Chandler's) that has a comprehensive supply of air conditioning parts at discount prices, and picked up a new shaft seal and port seals for the compressor, as well as a pint of ester oil and three cans of R-134a. In the second small error, I turned the clerk down when he offered to sell me a gasket set for the compressor. Next, I went to A.I.R. auto air-conditioning warehouse and bought an adapter to allow me to connect the stupid new charging hose to my vacuum pump. Finally, I stopped by the library and picked up a copy of Automotive Air Conditioning, by Boyce H. Dwiggins, to find out how much oil to use (10 oz.) and how tight to torque the bolts on the compressor (14-19 ft-lbs).
Then I went home to do the work. I removed the compressor, cleaned it up and poured out all the old mineral oil. Discovered that the shaft seal was the wrong type, so went back to Chandler's to exchange it (not their fault, really -- the seals can only be matched with certainty by comparing them side-by-side). Finally got the compressor back together with the new ester oil, port adapters and seals in place. Installed it on the car, vacuum-pumped it, installed R-134a, tested it, and I was finished, right? Yes, until the next day, when I found the new refrigerant had all leaked out.
An hour of testing and listening for leaks with my trusty Sears mechanic's stethoscope confirmed that I needed to replace the compressor head gasket and valve plate gasket. I could hear the refrigerant escaping through one of the bolt holes for the low side service port. Another trip to Chandler's, another vacuum and recharge, and I was finished. Again.
The next day in my air-conditioned comfort I could hear a strong rattling from the front of the car whenever the engine hit 2,500 r.p.m., so I checked it out that evening and found that the compressor was vibrating at that speed. Not just a little. It looked like it would tear itself off the engine inside a week. Ah, thought I, maybe this was what was meant by the rumor that the B-20 air conditioner brackets are no good!
The more I studied the setup, the less respect I had for the brackets. There seems to be no support to prevent the top of the compressor from vibrating lengthwise with respect to the engine. And that's what it was doing, to the tune of a half-inch in either direction! A half-inch may not sound like much, but this thing is held to the brackets by no less than six hefty bolts. Any movement should not be noticeable.
I first decided to use the later B-20 brackets when I discovered that my rebuilt late B-18 had the appropriate holes in the block. The main reason I decided to switch from the old style brackets was that I didn't like them, either. They always did the job, but there was evidence that they had come loose in the past. And they interfered with access to the timing cover and the oil dipstick.
However, that now seemed like a small price to pay, so I rounded up the old brackets (never sell anything!) and added the one that goes from the top of the compressor to the forward distributor bolt. Since that one provides the lengthwise support that's missing from the later brackets, I saw no reason to replace them. That stopped the vibration, and I have air conditioning once again.
One last observation from this experience: The name, Freon, was copyrighted by DuPont many years ago. The generic term, of course, is R-12, but nobody ever used it until the present conversion hassle began. So what's DuPont's new trademark name for R-134a? Is it Superon? Ozosafe? Coolite? No, it's Suva. Something tells me it won't catch on like Freon. Go to your local auto supply and ask for a can of Suva. You'll see. They'll send you to Eckerd's.