jomosc400

my 93' sc400 is still equipped with the r12 a/c system. took it to my mechanic today who gave me the impression that converting it was the way to go.
Pros: easy conversion, product readily available, no need to be a licensed r12 a/c specialist to do the work.

So here's my question ..

What are some of the cons?

Duck05

I had my '92 SC300 a/c converted by a local shop. It "lasted" about a year or so due to poor installation of the O rings (r134 molecules are "smaller " than r12). The gas eventually leaked out.

Took several tries by another shop (even after the major components - compressor and condenser - were replaced). And even then, I am looking at a recharge again.

R134 systems are not as cold as R12 (I have read - I really had a hard time measuring that...).

But, the recharging process is quite fast and the service is readily available - some advertise a "$20" version but a shop (with the machine) typically charges $60-70 (in California).

My advice is to try and get the install of the conversion kit warranted for 2 years against "leaks" (if a shop will even consider it).

I am sure others will have more or better advice....

mecheng10

personally from what I have seen/read, it might take more money and time to go to a r12 specialist, however very rarely do the swaps work as well.
there are issues with leaks almost every time.
it takes the engineers a great deal of time to design the HVAC system for a car, and it works for a specific material.
you will probably have to replace the condenser (bigger one) the fan (a bigger one)
and you have to make sure you get every last bit of r12 out, or else when mixed with r134 it turns into a jello like substance. rather nasty.

so most likely you will have to replace every part of the system.
not worth it imo.

Lexman4375

The only "cons" that I can think of is that its not very cost efficient to convert. I initially thought about doing that with my 95 SC4,particularly because I live in Africa hot Houston TX lol. I went to Autozone and bought their r-12 recharge kit for $40 and did it myself. The directions were clear and easy to follow. The kit came with a gauge mounted to the bottle. The AC will run you out of the car now. That was over a year ago. I wouldn't hesitate to do it again as long as there is no significant coolant loss after charge#1.

Bdub215

iTrader: (1)

134a is about 10-15 degrees warmer then R12. That probably my only con for 134a.

R12 is few and far between and al gore will hate you if you vent it to the atmosphere.

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SC400slide

iTrader: (11)

I had my A/C converted from R12 to R 134a when I got my SC and it wasnt too bad of a job.

Granted, I had a brand new A/C compressor in the trunk, so I didn't need to flush anything. Swapped out the old for the new, and put the "new" PAG oil that was for 134a. All the conversion changed was two schrader valve tops.

SpooledSC

iTrader: (1)

From what I have seen:
1) Isn't as cold.
2) 9/10 times it has leaks (mainly due to not replacing all O-rings, system isn't flushed all the way, and most cases a cheap ester based oil is used in conversions because it's "universal" between R12/R134A.)
3) R12 is very hard to find now a days and extremely expensive.
4) Not many shops will do it anymore due to above items.

Not saying it is always that way but a good majority of the time. I'd personally stay away from the conversion kits from AutoZone or any other parts store unless their kits include: a flushing agent, accumulator/receiver dryer (or desiccant bag), new orifice tube/expansion valve (that's made for R134A pressures), all new O-rings, and a standardized PAG based oil (mainly PAG 150 is a good "safe" weight.)

covert

So the guy I bought my car had no gas in the system because he disconnected it in doing the timing belt job (unnecessary, I did it with it connected)


Things to consider:
-refrigerant metering device:these 2 many times in refrigeration applications they are "close enough" and people can change gas with compressor change and leave the old capillary tube or txv. It's a good thing lexus uses a thermal expansion valve (txv) ahead of their time. My 92 chevy is just an orifice!

- fittings: I have refrigeration equipment, all i needed was the factory 1/4" flare on the suction line. didnt even need the 3/16" flare coming out of the cond. (is easily adaptable) for checking head pressure.
auto guys generally don't have these, but are easily available from any hvac store or pawn shop.

-refrigerant oil: r12used to use mineral and modern cars use pag...Usually one can get away with dumping some new oil from a can at the auto parts store.
I weighed in a r134a charge from my 30lb tank into my freshly vacuumed system and the compressor sounded fine and blew cold to my liking. It may have had a compressor change before, who knows, who cares. It works.



Pro tip: finely adjusting the grams of charge lower than the sticker says will lower your coil temp, but too low coil temp...it'll freeze/not work efficiently. And CLEAN your condenser and evaporator!! buy coil cleaner at your local refr shop spray a foaming can and blast w water!

At the same pressure 15psi a 134a evap coil is 15 degrees while r12 is 17.7deg F, higher pressure = more compressor load= more engine load = R134a is colder and a more efficient use of belt HP!!!

RXRodger

iTrader: (2)

I know this is an old thread, but why do people post erroneous information like this? If you don't know something keep your mouth shut. Almost every bit of the above is not true. Mixing 12 and 134 does not make a substance like jello. The two oils might do that if you don't get the old mineral oil out, but the 2 gases do nothing of the sort.

You do not have to replace every component, this is just not true. Many systems, including ours, can be converted and have enough margin of error in the sizing to more than cover the differences in heat transfer requirements.

They do not leak just because you convert to 134, they leak because there is something that leaks. I even see in one of the previous replies "the molecules are smaller". Where do people get this stuff? Why would you have this conversation if there was not an initial leak? The elastomers get old and they leak. Due to the slightly higher head pressure sometimes leaks develop on the high side at old orings with 134 because they are old, not because it has 134 in the lines.

So, once again, beware of what you read on the internet, above quoted example case in point.

Returd

I'm now getting into the conversion for my 92. Is there a list or diagram of all the seals. I'm thinking that just based on age alone \i should replace all the seals. (please don't tell me there's one between the motor and firewall)

RXRodger

iTrader: (2)

I can go lay hands on the evaporator with expansion valve, epc valve, etc and take a pic if you want to see where the connections are. But, if it's not leaking, in my opinion don't mess with it. See your other thread for info on that part.

Returd

Thanks, I'll investigate on my parts car. I won't say no if it's easy for you to take a photo though.