It’s hard for me to believe that it’s been eighteen years since my series of columns entitled “Conditioning The Coupe (Part XX of 700)” ran in Roundel. In those columns, I described the from-scratch retrofit of air-conditioning into my 1973 3.0CSi. I’d done a/c repair before, but this was much more involved. I worked with a vendor who advised that I go with an R134a system since Freon (R12) had already been on the outs since the early 1990s, and its long-term availability was questionable. To maximize the system’s performance, we took the extraordinary step of having a custom evaporator core fabricated; it was the same size as the original core but had twice the number of passes of the cooling tubes through it.

    I found an original E9 evaporator assembly and the all-important plastic duct connecting it to the vents in the center console. The vender sold me the custom evaporator core, a rotary compressor and bracket for the M30 engine, a condenser, a receiver-drier, and a few other small parts. I paid someone to fabricate the hoses, and paid someone else multiple times to pressure-test the system, locate leaks, evacuate it, and recharge it.

    After some initial teething pains, the system has remained functional for all these years. However, although I love having an air-conditioned coupe on long trips to the Vintage and other shows, the truth is that the system’s performance has been adequate—but not great. In contrast with Freon-based systems which you turn on and they immediately blow cold, R134a conversions often take a while to spit cold air at you, and quite a bit longer to actually chill the interior of the car. When you combine that with a hot car that’s been sitting in the sun, the results can be disappointing. Even once the E9’s interior was cooled off, the car’s a/c would get overwhelmed on the stretches I’d routinely hit on the way to the Vintage, where the temperature was 95ºF with 90% humidity.

    Over the years, I took a number of steps to mitigate the intrusion of heat into the cabin. I re-lined the foam on the heater box flaps to block off hot outside air, tinted the windows, and installed a valve to stop the flow of antifreeze to the heater core—which, unlike the one in a 2002, is always plumbed with hot antifreeze; the heater-control lever merely opens up a flap to direct that heat from the heater box into the cabin.

    These things made some difference, but the E9’s a/c has never been bone-chilling cold.

    Fast-forward to now: I know a lot more than I did then. I now do all of my own a/c work, including hose fabrication, leak-testing, evacuation, and recharging. My next book may well be The Hack Mechanic Guide To Vintage Air-Conditioning. I know that, as cool as my custom double-pass evaporator core is, it probably wasn’t necessary, as evaporator performance usually isn’t the limiting factor of a/c performance; condenser performance usually is. I know that the type of serpentine-flow condenser that’s original to any pre-1990s car—and that was part of the retrofit into the E9 eighteen years ago—is now obsolete, and that any a/c retrofit or rejuvenation should include a modern parallel-flow condenser. Rather than having a single serpentine tube snaking through it, a parallel-flow condenser employs dozens of tubes acting in parallel to maximize the transfer of heat, thus increasing thermal efficiency—and thus cooling. I know that the advice now is that if you’re going to run R134a in a system originally made for Freon, if you don’t also upgrade to a parallel-flow condenser, you’ll likely be disappointed. And I know that the reported death of Freon was exaggerated; it is still available, although it is increasingly difficult to find commercial shops who will work with it.

    With this knowledge, I’ve actually taken things a step further. Both my ’72 tii and my Bavaria—whose a/c systems I’d rejuvenated by installing the biggest parallel-flow condenser that’d fit in the nose, installing the biggest fan that’d fit on the condenser, replacing the ancient upright piston compressor with a modern rotary one—are charged up with good old-fashioned Freon, and they get cold enough to hang sides of beef inside. You want a recipe for a cold car? It’s right there.

    In addition to the E9 being equipped with a now-obsolete serpentine-flow condenser, I made a mistake when I installed the condenser in 1999. When I went to get the hoses made, the fabricator (Ed Ellis, from “Ellis the Rim Man” on Comm Ave for you old-school Bostonians) discovered that I’d accidentally mounted the condenser upside down, with the #6 fitting at the top and the #8 fitting at the bottom. I should’ve just gone home pulled it out, and re-mounted it the correct way, but I had an appointment, I was there, and I wanted to get the hoses made. Fortunately, Mr. Ellis was able to make hoses with step-up and step-down fittings. He said that it probably was a non-issue, but I’ve always wondered if it was one of the factors limiting performance.

    So for eighteen years, the cooling in the E9 hasn’t been great, and I’ve second-guessed the use of R134a, especially since the tii and the Bavaria, which both run Freon—and which I rejuvenated after the E9—perform so well. For all these reasons, I’ve been itching for a reason to yank that serpentine-flow condenser out of the E9, replace it with a modern parallel-flow unit (installed right-side up), evacuate the system of R134, charge it up with Freon, and right the wrong I did eighteen years ago.

    After I attended the Vintage in 2013, I thought I had my chance.

    You may recall my story of the Great Drenching Event, where I explained how I hit a solid 500 miles of torrential rain on the way to Winston-Salem. During the deluge, I saw something skitter off the back of a truck and then heard an alarming smack in the nose of the E9. When I stopped, I found that a clevis pin and chain had smashed through the E9’s front grille; the pin itself, a bit larger than a lipstick tube, had impaled the condenser. Miraculously, it embedded itself between two passes of the serpentine tube without puncturing it. But it did get me thinking about planning the condenser’s replacement.

    Oddly enough, it was the E9’s sister car, the ’72 Bavaria, that was ultimately responsible for the E9’s finally receiving its parallel-flow condenser. When I bought the Bavaria a few years back, its a/c wasn’t working, so I embarked on my standard resurrection process that’s all but guaranteed to result in a cold car (big condenser and fan, rotary compressor, all new hoses, Freon). As part of this process, you need to identify the biggest condenser that’ll fit in the nose. It’s clear from the photo below that the E9’s eighteen-year-old 16"x20" serpentine-flow condenser fit with gobs of room to spare, so in addition to going parallel, I wanted to go up in size.

    You can look on enthusiast forums and see if there’s an agreed-on maximum condenser size for your model, but Bavaria forums aren’t as active as, say, 2002 forums, so I measured for myself and bought a 16"x22" condenser. As is often the case, though, once the mounting brackets were installed, the hose fittings didn’t have clearance, and I had to fall back to a 16"x20" condenser for the Bav. However, a quick set of measurements in the nose of the E9 showed that that 16"x22" unit probably was the right size for E9, so rather than returning the condenser, I held onto it.

    For three years.

    Early this summer, I finally rolled up my sleeves and had at it. Out came the E9’s radiator and its serpentine flow condenser. I test-fit the 16"x22" parallel-flow condenser with a pair of “short-drop” hose fittings on it into the nose, and verified that it was indeed the right size. As a rule of thumb, the actual width from the left-most edge of the condenser’s mounting rail to the right-most edge of the short-drop fitting adds about 3" to the quoted width of the condenser. The 22" condenser, with 3" added for the brackets and fittings, comes to 25". In the E9, there is about 27 inches of space side-to-side in the nose. That leaves 2" for mounting brackets and getting the hoses on. You can try getting another inch out of it, but leaving 2" of space is a safe plan.

    I could’ve moved up in size from the 14" Spal fan I’d installed eighteen years ago to a 16" fan, but to save money, I reused the fan, zip-mounting it to the new condenser. I have mixed feelings about this, and have mounted fans different ways on different cars, but these low-profile Spal fans are fairly light, and I haven’t had any problems using this simple mounting scheme.

    I went to great pains to mount the new condenser in the E9 by re-using the mounting holes I’d drilled eighteen years ago. (Nowadays I’d never drill holes in the body panels of a 2002 or an E9, but, hey, they were already there.) Once I began to carefully line things up, though, my initial reaction that “it fits fine” was tempered somewhat. I’d originally shock-mounted the previous condenser using the same rubber mounts with threaded studs used on tii fuel pumps, but for a number of reasons, the new condenser needed to be stood further out from the nose panel, requiring me to use fixed metal spacers for stand-offs. I also needed to cut a few inches off the bottom right corner of the condenser’s mounting bracket to clear a piece of sheet metal in the lower corner of the nose.

    I assumed that I’d simply re-use the old mounting brackets, but one of the maddening things about these universal condensers is that their hole spacing is not standard; some have a ½" hole spacing, some use 9/16". In this case, the old brackets had a different hole spacing than the new condenser. The result is neither pretty nor elegant, but no E9 was further harmed by drilling during the installation of this condenser.

    With the condenser mounted, the next task was adapting the hoses. I was thrilled to find that I was able to cut off both the lower and upper hose fittings from the condenser hoses and crimp new ones on in place.

    Then it came time to address the question of converting the system to Freon. There are many issues here, and I’ll leave most of them for my next book—I was quite serious about the book—but, long story short, when converting between R12 and R134a, you need to remove all traces of the old refrigerant and lubricant, and that means flushing the system, and that means removing the evaporator assembly from up under the dash and disassembling it so you can flush the evaporator.

    Removing and installing the evaporator assembly in the E9 is one of my least-favorite automotive repair jobs. It’s nerve-wracking; the ductwork is 43-year-old plastic, and it cracks and then shatters if you look at it the wrong way. The vinyl on the sides of the console tears easily. And the side pieces of the console are made from ancient particle board that spontaneously dissolves like doppelgangers of lovers in 1970 horror films. No, on more careful reflection, I was not going to pull that evaporator out unless I had reason to, like it was leaking. The R134a had a reprieve—for now.

    I replaced the receiver-drier, pressurized the system with nitrogen to leak-test it overnight, and in the morning found that the pressure was down. Using Big Blu soap solution, I discovered a leak in the hose fitting on the other end of the lower condenser hose—the end that still had the original fitting. The hose didn't have sufficient length for me to cut that fitting and re-crimp it, so I made another hose and installed it.

    I then pressure-tested the system overnight again. When I was convinced that it was leak-free, I evacuated it and recharged it with R134a.

    So, although cost-wise it was easy (the parallel-flow condenser cost only about fifty bucks), needless to say this was not a plug-and-play operation. And the results are… okay, but not transcendent. Once I’m under full sail, I’m seeing 43ºF vent temperatures. The system seems to run a little colder than it did before, and perhaps cools down a little quicker, but it still doesn’t come close to the instant-on, freeze-your-knee-caps quality that the Freon-equipped tii and Bavaria have.

    Of course, that could be due to some other issue. The system might not be properly charged. The expansion valve might be sticky. And there’s no question that the blower fan in the evaporator assembly is a little anemic.

    But really, this is all the warm-up—the cool-down?—to the bigger show, which is a from-scratch retrofit of a/c into the Euro ’79 635CSi, a process that is already under way, one piece at a time. I face the same R12/R134 issue. Some folks have been trying to bend my ear on R152a. I’ll begin writing about this soon.

    The editor and I both hope the series will have fewer than 701 installments.—Rob Siegel

    Rob’s new book, Ran When Parked: How I Resurrected a Decade-Dead 1972 BMW 2002tii and Road-Tripped it a Thousand Miles Back Home, and How You Can, Too, is now available on Amazon. Or you can order personally inscribed copies through Rob’s website: www.robsiegel.com.