R12 to 134 back to 12

[Guest Plata]

OK Boys and Girls, here is a challenge for you. 1978 Ford F-150 with factory air, new Sanden compressor, o-rings, hoses, exp valve and dryer. Running R-12 cracked a fitting while on the road and lost all freon. Repair shop in Chicago could not do R-12 so they squirted 134a into the system and sent me on my way. He claimed that my new compressor probably had compatible oil so no worries. After running that 134a for about 2 years I would like to go back to R12 so I can get my A/C performance back in this 100 degree Texas heat. Can I just evacuate the system and put R12 back in? At high idle I am running 25psi on the low side, jumps to 40 at slow idle. Just NOT cooling the way I would like. Thanks for your guidance...Terry

[Guest]

OK Boys and Girls, here is a challenge for you. 1978 Ford F-150 with factory air, new Sanden compressor, o-rings, hoses, exp valve and dryer. Running R-12 cracked a fitting while on the road and lost all freon. Repair shop in Chicago could not do R-12 so they squirted 134a into the system and sent me on my way. He claimed that my new compressor probably had compatible oil so no worries. After running that 134a for about 2 years I would like to go back to R12 so I can get my A/C performance back in this 100 degree Texas heat. Can I just evacuate the system and put R12 back in? At high idle I am running 25psi on the low side, jumps to 40 at slow idle. Just NOT cooling the way I would like. Thanks for your guidance...Terry

Providing everything is like it was before the 134 was installed would be no problem. I would take the reciever drier out and put it in the oven for a few hours to get rid of as much moisture. I assume you have a vacuum pump and manifold gauges to do this properly.

FWI natural and physical scientist have now found out that one volcano of very modest size with a average eruption cycle produces more CFC's than all the CFC's ever produced by humankind with R12 freon. Lets all go over to Hawaii and plug up that Kilauea. It's depleting our ozone layer.

Don

[Guest Plata]

Thanks for the reply Don, Removing the dryer would be impractical, but since it is 105 degrees here in Texas today that should do the trick! I do have a vacuum pump and gages for both 134 and 12 so all set there. I think I will pull a vacuum and let this sit overnight. Question on charging with R12: I have a 20 lb drum. do I charge with vapor or should I tip the drum for a shot of liquid during the initial charge?

[Guest]

Terry, even though it's 105 degrees (and I know Texas) the baking is to get the moisture out of the dryer. Good question on the re-charge. As you probably remember we would charge a system with cans in the upside down fashion, but charging stations cannot do it this way and they seem to work OK too and their bottles were straight up. Also the beauty of R-12 when charging is you know the system is full when the bubbles in the sight glass stop, unlike R134 where you really have to measure the amount of poundage and not take notice of the sight glass.

Don

Edited August 11, 2010 by helfen (see edit history)

[Larry Schramm]

The vacuum pump and left overnight should do the trick. If not, put in a new receiver dryer.

[Ron of Chicago]

Having the system in a vacuum for 30 minutes should remove all the moisture. As long as the system holds the vacuum (after you shut the pump down and close the system) then you should have no problem re-introducing R12 back into it.

One thing to check. When the system was changed to R134A did they change the pressure switch? (I think that needed to be changed on my Lincoln to reset the pressure). If they did you may have to get the correct one back on.

I changed my Old Lincoln to 134 and just added the PAG oil and replaced the switch and remember it did not cool as well as the R12 at idle either. My 01 Chrysler does not cool well at idle either.

Good bits of information on the Volcano Don. If you would like to send me a ticket to Hawaii I will be glad to meet you there to help , ha,ha.

Ron

[Larry Schramm]

I almost forgot to mention was that when the system was changed over to 134A they probably put the new style ports on the high and low pressure fittings. If so, that could be a problem, especially if someone else ever works on the system. The R12 system has the screw on connections and the R134a has the quick connect. They are made to be non compatible.

[51dyno]

R12 oil is not compatable with 134 - 134 oil is not compatable with R12. Did the guy flush the system before installing the 134 if not that could be part of the problem-did he change the O rings at the conections-did he change the dryer?????????This is what is tought to get your Fed. Liciense.

[Guest Plata]

All, Thanks for all the feedback! To answer a few of the questions and describe the situation: When the original York compressor threw a rod I replaced it with a new Sanden. I made new hoses, replaced the O-rings, new dryer, new expansion valve (R134 valve, R12 was not available) and blew out the condenser core and evaporator with solvent. Then put in fresh R-12. Ran great then broke a fitting in Chicago. (Ron, actually in DesPlaines). The little shop on Rand Road could not supply R-12, so we JB welded the fitting and put in R-134 to get me home. He claimed that the new Sanden compressor probably had compatable oil in it already. It cooled acceptably for over 2 years then our JB repair failed. So I Just made a new hose to replace the broken one, used R-134 fittings, charged the system and it just does not cut it. Seems worse than before especially over about 95 degrees ambient. Oh, there is no pressure switch in the system, R-12 did not need it and since I rebuilt the system for R-12 I did not install one. Now I am at the point of my original post, wanting to go back to R-12. Larry, I am not concerned about the quick connect fittings because they will screw on to the ends of my R-12 gauge hoses. Well that's all the history guys. What do you think? Terry

[Guest]

Just a FYI some cars that were produced for R12 did have low and high pressure switches. The reason for that was the re-design of compressors that did not have a oil sump anymore. The system relied on a continual amount of oil circulating in the system like R134 systems. If the system had a leak and did not blow cold customers would keep that A/C switch on anyway and with no oil would burn up the compressor. Even though the old compressors ( GM six piston ) are heavier and use more horsepower they really last, even when people run them with no freon.

Don

[Dave@Moon]

The little shop on Rand Road could not supply R-12, so we JB welded the fitting and put in R-134 to get me home.

Terry, this almost certainly violated Federal law and is subject to a HUGE fine. Anybody with a license to collect R12 will have the equipment to store and re-install it. Real R12 stopped being manufactured 15 years ago. It's not something you can just go out and buy and refill no matter who you are. If they didn't have a stored supply of R12 onsite, they were almost certainly unlicensed.

Unless you've been running a combination of R12 and R134a for the last 2 years (impossible if the system kept working, see: R12 to R134A Refrigerant Retrofit), this shop had to have bled the R12 into the atmosphere. Had they been caught it would've been the end of the shop.

My guess is that when they dumped the R12 and purged the system with R134a they managed to blow enough of the R12 oil out to save the system (and the R134a charge came with it's own oil charge in it, whether they told you about it or not).

Most importantly, if the system was running O.K. with R134a before the JB Weld failed, then it should be doing so now as well.

I strongly recommend that you recharge the system with a can of R134a that contains a dye for detecting leaks. It's available pretty much everywhere. If the system is fully charged already but is not cooling correctly, then something got damaged (mixed oil, JB Weld in the system, water contamination in the receiver, etc.). Reinstalled R12 isn't going to fix a mechanical problem, and will cost more (legally installed) than a mechanical repair anyway.

[Ron of Chicago]

I agree with Dave@Moon. You say that the system worked well for 2 years until the fitting blew. I would think that it should work well again once you get the fitting repaired properly.

Seeing you are already set up for the 134 why don't you keep it that way and sell the R12 you have to pay for any repairs?

Do you remember the name of the place on Rand Rd.? Just curious is all.

134 is not expensive and you can get it at any auto supply. Suck it down real good and put a couple of cans in. See what happens (after the repair). See what you get for gauge readings.

Ron

[rhb1999]

51dyno is right, R-12 mineral oil is not compatable with R-134 oil, and he is also right that the system should have been flushed out with an flushing/cleaning agent. By law, the A/C tech man should have installed barrier hoses on the system to compensate for the higher head pressure of R-134. Online automotive A/C forums have told me that it's illegal to change a R-12 system that has been retrofitted to R-134 BACK to R-12, but this was NOT on the test when I took it. A new ruling? It's possible you could flush out the system yourself (you may need a compressor) first recover/remove the R-134 if you don't have a recovering machine, take it to an A/C shop, ( it's illegal to vent any refrigerent) buy a flushing agent and then remove the evaporator from the firewall (to get all of the flushing agent out, by tilting it after flushing). and do the same thing with the condensor. I don't know if it's wise to run flushing agent though a compressor, I would let it drain out, turning it every so often to try and get all of the "oils"out. Replace the hose assembly (I also don't know if I would flush the hose assembly,some of them have a muffler, a metal can that might be hard to flush out also read to see if the flushing agent is harmful to types of rubber hose) and the drier, reassemble using R-12 mineral oil on the new "O" rings. (not too tight on the connections, count the number of turns when removing). Evacuate and recharge with R-12. Hope this helps.