1966 Oldsmobile A/C

[Carguychris85]

If you think R12 is expensive, wait until you price R1234YF. R1234YF is being used on a lot of new vehicles.

R1234YF far outperforms R134a in the vehicles I have been in using it. Instant cold air and sill turn the interior into a meat locker.

[Carguychris85]

I advise staying far away from the highly flammable refrigerants you mention: R-152a, propane, and isobutane. They're very dangerous to work with, present a fire hazard should the system leak, and they're just not worth the risk, in my opinion.

As already suggested, R-12 would be best because your system was originally designed for it.

R-134a will also work, is much less costly, and readily available for the foreseeable future. But it will have a slight penalty in cooling efficiency in your application.

If you decide to go with the latter, be sure the desiccant in the receiver/dryer you install is compatible with R-134a, that you evacuate the system well (several hours and even overnight), use the correct amount and type of oil (PAG-46 or PAG-100), and charge it to about 80-percent of the R-12 amount.

With lines being made anyway, he can actually make the R12 system perform better than R134a than it did with R12. The STV needs to be recalibrated or eliminated with a STV elimination kit (the way I would do it) and the car needs the largest parallel flow microtube condenser that will fit installed. Biggest issue with R134a is getting the heat out of the condenser. It is very important to have a strong fan clutch and the largest fan with the most aggressively pitched blades that will fit the shroud. Some later 80s and early 90s Ford applications used a standard CW rotation plastic fan with 9-11 blades and it is the same diameter as the old GM 5 bladed steel fans. It moves much more air especially at idle. I have had 2 different R12 era G20 vans that will blow 30F on a 115F day before the compressor cycles using R134a and when the cycling switch on my 87 failed in the closed position it turned the evaporator core into a solid block of ice in about 10-15 miles. The vents were blowing in the mid 20s before it froze the core.

[Carguychris85]

I just looked up the part number of the Ford fan I run on my 1983 G20 with a small block 406 in it. It is Dorman 620-148 used on the 3.0L V6 Rangers in the 90s. Clockwise rotation, 18" diameter, 12 blades, same 3.25" bolt circle as a GM clutch, same 2.62" mounting diameter where it centers on the clutch. I had to slightly drill out the mounting bolt holes as Ford used a M6 bolt and GM a 5/16" but that took all of 5 minutes using a step drill. It moves much more air than the 5 bladed GM fan which greatly reduces the ac pressures at idle and lower speeds. As a bonus the engine runs cooler in hot weather with the load of the AC on it and the fan itself is much quieter as the severe duty clutch I run seldom has to fully engage. Even sitting at idle in 115F with the dual evaporators the system will hold low-mid 40F out of the vents at idle in 115F ambient temps. I used a Peterbilt application microtube parallel flow condenser that was the largest unit that fit the core support opening. It is almost as large as the 28 x 17" radiator core behind it. It is sealed on the top, bottom and sides to the radiator with 2" blocks of foam rubber insulation for window units. The insulation I bought came with 3M peel and stick adhesive on one side, which I stuck to the condenser on the outer edges of the core. When the condenser was installed it sandwhiches nicely against the radiator sealing the gaps, forcing air to be pulled entirely through the condenser rather than around it.

My 1987 G20 with a L31 350 in it has the reverse rotation equivalent of the same fan design, it is for a 2006 Ford F150 with the 5.4L 3V. It is dash air only and cools very well. The 87 does not cool as well at idle though, because the 4261 Sanden SD7H15 does not have the idle BTU capacity of an A6. I may replace that Sanden with a Four Seasons 10 cylinder HT6 upgrade at some point. That specific HT6 replacement is 210cc displacement vs 155cc of the Sanden. In hot weather it makes a considerable difference as the Sanden is barely adequate to pull a large GM single evaporator core and struggles at idle.

[JohnHere]

Carguychris85: This thread is more than four years old, so I doubt that people will see your current posts. Consider starting a new thread in "Automotive Air Conditioning Procedures, Tips and FAQ."