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Compatibilty of R134 and R12 systems?

andyb on Mon September 07, 2015 11:59 PM User is offline

Year: 1994
Make: Toyota
Model: pickup


I recently bought a '94 Toyota truck and as a part of the deal came parts to install AC (truck originally came without). The parts came off a '91 truck. I have most of the parts except a condenser. The parts are all originally R12.

My question is: can I buy a new condenser that is designed to fit a '91 truck? I know that the fill ports are different between R12 and R134 - are the fittings between AC components otherwise compatible? My concern is that a newly manufactured condenser made in the era of R134 will not be compatible with a system that was originally R12?


mk378 on Tue September 08, 2015 8:30 AM User is offline

The only difference may be the size and placement of the line fittings.

But, you should use the later model condenser. R-134a is harder to condense than R-12. Thus the condensers were improved for the 134a models.

GM Tech on Tue September 08, 2015 8:33 AM User is offline

You can still buy parts- there is not that much that changed that you would notice-- big concern is how do you interact your a/c controls with the truck's computer- if at all? Good Luck-

I never recommend transplants for this very reason, If you want a truck with a/c, buy one with it OEM- otherwise you end up with a cobbled up mess- with little or no high pressure, low pressure, cut-outs- engine rpm increase, stall savers controls etc.....relays aren't there- cooling fan will not be adequate, or sluggish- control head wiring can be an issue- just a big nightmare to do it right.

Toyota cars use an a/c amplfier- trucks most likely do as well- so you need to wire that in as well to do it right- otherwise, you'll have toggle switches and loose wires under the dash..

The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

Edited: Tue September 08, 2015 at 8:35 AM by GM Tech

NickD on Tue September 08, 2015 10:32 AM User is offline

88 Toyota Supra Turbo uses only 28 ounces of R-12 and will freeze your butt off. If you want to switch to R-134a, just about have to change everything for both cooling and compatibility issues. Including the hoses, TXV valve, ports, condenser, and even the compressor due to the higher acid content of PAG. Evaporator can stay.

Have to be 608 certified to buy a can of R-12, but even my six year old granddaughter can pass that test, just have to know the meaning of the word recover, don't have to know a single thing about MVAC.

Your choice.

mk378 on Tue September 08, 2015 10:37 AM User is offline

For tax reasons, the A/C systems were designed to "bolt on" by a dealer. All trucks had the necessary "hooks" in the computer and harnesses when they left the factory. If you get ALL the parts necessary off of an A/C equipped parts truck, it is plug and play. Though mixing different years could be an issue.

Technically it would not be legal to run R-12 in a 1994 (post-ban) vehicle even if you have some parts from older trucks on there.

And hi'ya Nick, long time no see.

NickD on Wed September 09, 2015 6:28 AM User is offline

Yeah, EPA calls this a sham retro, converting an OE R-134a system to R-12, fined the heck out of several shops for doing this. Another bad joke was dealer installed AC systems, had more parts left over the consumer had to pay twice for, and most of the mechanics didn't know what they were doing.

Dealer installed options are coming back, another trick so dealers can make more money. Was thinking about becoming a certified floor mat installer.

Banning R-12 was instantaneous based on a theory, even though less than 2% of the total CFC production was used in MVAC. And the burden was put on the consumer for the retro. Asbestos was another known cancer causing banned product, but one of the main uses that really put harmful dust in the air such as brakes and clutch discs, gave them a much longer time to find something else. But a tiny piece of asbestos in say a hair dryer was recalled practically bankrupting every company that was using it.

Extensions were given to several auto makers to convert to R-134a, wonder how much money they paid to the EPA. So what's in this 1994?

Cussboy on Wed September 09, 2015 8:23 AM User is offline

My 1988 Mazda B2200 truck has the dealer-installed AC, and in the 21 years I've owned the truck the AC has worked pretty well (Arizona, 207K miles). Yes, it has been through at least 4 compressors and one evaporator (hole) purchased through this board's sponsor, but does get used a lot, and still R-12. It's VERY well coordinated with the system, but this is not a computer-controlled vehicle either.

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