R12 & R134a Retrofitting & other A/C info

Gro Harlem · Post by **Gro Harlem** » January 31st, 2006, 3:50 pm

I'm in the process of taking apart my drivetrain & stregnthening the tranny internals & LSD and since half the stuff under the hood is taken out I figured I' see if i can find the leak to my A/C.

Anyways...my a/c USED to work when i first had my car...it worked amazingly well. Probably the coldest i've experienced in any car. Then, last January, I re-did my engine swap and painted the engine bay at the same time. After I did all this....the a/c no longer worked, i guess I bent a line or the rubber hose on the compressor sprung a leak.

I lived last summer without a/c and it was one of the main reasons I stopped driving my MX pretty much entirely after May & bought a car with a working A/C (my 96 pos protege).

ANYWAYS. I've been doing research & there seems to be TOO MUCH misinformation relating to R12, R134a & whats compatible & what isn't & what needs to be changed.

The majority of the "help forum threads" i could find were in relation to OLD OLD 1970-1980's cars that people were "fixing up" or restoring & wanted to retrofit b/c of the ridiculous R12 price. Almost all of those always mentioned having to change out the compressor seals & other o-rings & seals b/c they weren't compatible for some reason b/c they are made out of some crappier material that will dissolve over time.

1st question
Anyone know if the MX-3's seals will be fine with R134a? I figure since ONLY the 92-93 models used r12 that the seals would be engineered with the new R134a laws in mind so they wouldn't have to redesign the compressor & a/c lines, etc.

2nd question
I heard a lot of crap about how you need a new evaporator, condensor, even a new compressor. R134 runs at a higher pressure, thus the compressor apparently works harder. I personally think that since our car is small in terms of interior volume...and the compressor is the same one used on much larger mazdas & even fords that the compressor is overkill for our R12 system as it is...so it should be able to reliabiy handle R134a. Does anyone know for sure?

3rd question
Relating to compatibility, i couldn't find JACK about WHY it matters to not mix mineral oil (the oil in r12 systems) with R134a refridgerant. All I read is "drain it all out" or "don't let it cross-contaminate". I'm one for explanations...WHY the hell does it matter? what happens exactly? I wish these dumbass sites would mention this..especially the ones that are selling products.

On a related note, I read that "ester-oil" is compatible with both R12 and R134a, and the retro-fit kit I just bought has cans of refridgerant with the ester-oil already inside. But for some reason this kit doesn't mention anything about "drainig out all the mineral oil", and It almost makes me want to assume that ester-oil somehow magically makes the mineral oil work fine with R134a. I also read on numerous websites taht this exact kit I bought (interdymanics..from pepboys...31.99) worked "great" and required you to basically screw in the special fittings....and charge up your system according to the directions...nothing else.

So last question:

What should I do exactly?

I'm thinking of just using the retrofit kit i just bought...fill up my system with the r134a (not caring if there is still mineral oil & r12 inside) and THEN use a UV kit that is compatible with 134a and find the leak. Fix it, then properly evacuate teh system, drain the compressor of mineral oil (i'll have to figure out how to do that..doubt its too hard) and re-fill with another charge of R134a.

Sound like a plan? or am I missing something here that will waste my time/money?

ariesdude · Post by **ariesdude** » January 31st, 2006, 5:31 pm

I think R134a molecules are smaller than R12 - so there is a possibility that previously good seals and o-rings might develop a leak with the new refrigerant. Considering that the seals/hoses/o-rings are 13 years old and possibly leaking already it might be a good idea to change them. It will probably save you from continuosly looking for leaks with a UV light...

If the compressor was working fine before - it probably will work fine. But the dessicants are different - so you must change the accumulator-drier. Its also recommended to change the orifice tube to make it more compatible with R134a.

The mineral oil will not mix with the R134a - it will be like an air pocket in water. For normal operation the oil mixes with the refrigerant and circulates throughout the system while lubricating various parts on the way. Imagine the compressor is pressuring the gas and suddenly encounters a pocket of high density mineral oil - something will break for sure. Ester oil on the other hand mixes freely with mineral oil and also mixes with R134a. Even ester oil could only do so much - you must drain all mineral oil - atleast as much as possible.

Also having both R12 and R134a is a bad idea - they have different molecular sizes and get pressurized to different levels and they dont mix. So the compressor will get a pocket of R12 and then get a pocket of R134a and so on and so forth - you can imagine the poor compressor kicking the bucket within say 5 minutes. You must evacuate the R12 completely - i think the procedure calls for vaccuming it out to a separate container or something like that.

IMO if you do it right the first time - it will be golden for some time to come .....

IMO you should take the components apart - blow air through them (or connect them to a vaccum pump or something) to purge them - replace some of the seals (especially the ones you took apart) and hoses - purge everything - put them back together with the special fittings and charge the new gas/oil/dye. If you get no leaks after that then you are almost done - otherwise good luck with the UV lamp...

FlyVFR · Post by **FlyVFR** » February 16th, 2006, 8:47 pm

I did my 92 MX with an Interdynamics retrofit kit about 9 years ago and have no problems at all.

Here is their website: http://www.id-usa.com/

kkyin · Post by **kkyin** » May 28th, 2006, 5:42 pm

how do I know how much R12 left in the system? I just know it's low on it, but not sure if it's completely empty so I can put r134a in.

Also, is the yellow cirlce the high side and the red circle the low side port in the picture?

Thanks all.

FlyVFR · Post by **FlyVFR** » June 22nd, 2006, 8:44 pm

kkyin wrote:how do I know how much R12 left in the system? I just know it's low on it, but not sure if it's completely empty so I can put r134a in.

Also, is the yellow cirlce the high side and the red circle the low side port in the picture?

Thanks all.

The R12 must be recovered by a licensed pro. FYI, It is illegal in the US to leak any R12 in the clear. The yellow circled connector next to the little glass window is High pressure.

G/L