Wrecked82

My R12 system needs charging. Interdynamics site says you can change over to R134a without having to change o-rings, hoses, etc. because they use ester oil rather than pag oil and is compatible with any residual R12 oil. So, question is, do you have to pull a vacuum or can you just charge up with the 134 if the system just "happens to be emply"?

markdtn

Yes, with any A/C system you must pull a vacuum. If you have much air in an R134 system the high-side pressures will go through the roof and you may have leaks.

Larry B.

You can get a vacuum pump from harbor frieght for $15 ... I you have a good compressor.

carnut114

I have done about 6 chang overs using the kit from walmart. Just made sure it was empty and put it in.

Eric

Pete76Shark

Yes you can.
Would I ? no,
Why, cause the R12 mineral oil is not compatible with R134a and it will not stay suspended. So what happens when the R12 oil does not stay suspended ? it separates and pools at the highest point in the A/C system, the evaporator.

Now I am by no means the expert on this, but more and more people and books say the same thing.
This is why it is important to get all of the old R12 oil out of the coils and hoses.

Will the old O rings leak with R134a ? Yes they will. Is this a big deal ? no I dont think so, but while your in there getting the old oil out you might as well install new blue O rings right.

Do you really have to replace the rubber hoses in the A/C system ? no, they may or may not leak depending on who you ask.


read this thread:
http://forums.corvetteforum.com/showthread.php?t=887121

Clint's C3

Some of the larger Auto Zones will lend you a vacuum pump w/ gauges for a hefty refundable deposit on the CC.

Lotus76

Eric, have you done this on Corvettes? I bought one of those Walmart kits and took the vette to an AC shop to have the R12 removed and he told me it was empty then tried to talk me out of going to 134A, he says it will not be cold. he also told me that my compressor clutch was way out of adjustment.

does anyone know how to adjust these or where to find AC serviceing information?

Thanks, John

Pete76Shark

You might consider buying a few cans of R12 on ebay, renting the Vac pump, pump out the system and dump in the R12. That might be the quickest way to get cold air out of the vents again.

carnut114

I did this on my 72 and it worked but then the clutch started to freeze up. The ac on was not hooked up when i bought it and the previous owner had the car for 15 years and never put a belt on it to try it. Then i installed headers and left it out. The other cars are still working fine though.
Eric

ewalker302

I've done the conversion to 134a on a (79'Bronco, 90'Mustang, 86'Maxima, 72'Mustang).

I just put the new stuff in. It worked fine everytime, just as cold, and no leaks if you didn't have any before.

A couple of these vehicles have been going 3yrs or more. The 134a kits/cans are so cheap, just do it and you prob wont have any problems.

You don't want to pay a lot for r12.....it won't be long bfore you can't find it on ebay or anywhere.

GaryS

There will be others that cringe but my friend "converted" his 73 BB by adding two cans of R-134a, one can of oil, and one can of stop leak to his original a/c system. He didn't pull a vacuum, didn't purge the old stuff, nuttin! Still works like a champ two years later.

When my 79 Mercedes, my daily driver, blew an a/c hose, I replaced the hose, used my Mity Vac to pull a vacuum (took about 11 gazillion pumps) and then refilled with one can of stop leak, one can of 134 oil, and two cans of R-134a. The a/c works VERY well inspite of reports that 134 doesn't cool as well and despite the fact that neither of us did any converting other than add the new stuff.

Third case. My nephew bought his grandpa's GMC work van, a 93 3/4 ton I think. The a/c didn't work. What recipe do you think I used to get it up and running? Yep! One can of stop leak, one can of 134 oil, two cans of R-134a. Three months later, it is still cooling off his van nicely.
Gary

djunod

Larry82, just have them recharge it with R12... don't do the conversion. It's just colder & more staying power... of course there are others that have fooled themselves into believing otherwise

flaskier99

I did the conversion on a '79. I wish I never had! The factory system is just not efficient enough for the R134. In the south florida sun and humidity, the converted factory system just can not keep up. I measured the cabin temperature before and after the conversion and based on my experience you can expect about an 8 degree (F) difference.

gliot1

Be aware that there are now environment safe R12 formulas (R12A) R12A is $15 a pound (a typical Vette uses 3lbs.) R12A can be intermixed with R12 and has the same properities as R12. I had mine done by a local hot rod shop who would do either the R134A update or simply add R12A. His advice was to go R12A as he claimed R12 still blows colder than R134. He claims that he has had great success with conversions, but felt I would be just as well off to stay R12 and it is cheaper than the conversion using the R12A. I read many articles on R12A prior to doing this and was convinced. This is not highly publicized because lots of shops and stores are making lots of money on conversion kits and conversion.

djunod

Thanks for the tip gliot1!!! I just drained the R12 from my Mako so that I could do get the A/C components out of the way... wasn't looking forward to the cost of refilling it with R12 again...

Do you have a link for online ordering of R12A?

Thanks!!!

marshrat99

[QUOTE=flaskier99

I did the conversion on a '79. I wish I never had! The factory system is just not efficient enough for the R134. In the south florida sun and humidity, the converted factory system just can not keep up. I measured the cabin temperature before and after the conversion and based on my experience you can expect about an 8 degree (F) difference.[/QUOTE]

I had my GM Goodwrench friend convert mine to R134 and it does run a few degrees warmer than I expected. But since it was not working when I originally got it, I can't tell for sure. I do know its not as cool as my liking but is OK.

Lotus76

Gloit1,
I would be very interested in getting more info on R12A. I purchased my vette with the system empty but closed so I am looking at what would be the best option.

Please send me a link if you have one.

Anyone know how to adjust the compressor clutch?

Thanks, John

Wrecked82

Somewhat on topic, what is the max pressure reading when recharging an R12 system?

ANother hint I picked up, on pulling a vacuum. Just connect the chargin hole to the low pressure and the other end to a vacuum port on the engine. Will pull an adequate vacuum when running a higher rpm to clean out system. Yes, freon, oil charge, water vapor will be sucked into engine, but not enought at once to make any difference.