Can I run R134 thru the old original A/C compressor?

[chevydog66]

I have a 72 GMC truck with factory A/C. I recently purchase the POA Update kit for R134, drier, and condensor for my truck. Will I be able to use the new R134 in my old original compressor? I know that the R134 operates at higher temperature and pressures. Will the old original compressor be able to handle it?

[Tynee]

I have converted a couple of vehicles to 134a without replacing anything at all. I'm not saying this is the correct way to do the job, but they were both valued somewhere right around $500, and I wanted air without spending an arm and a leg. Both compressors outlasted the rest of the vehicle.

I believe that if you replace the drier, and have the system charged by a professional who draws a vacuum on the system for the proper length of time prior to charging with the new refridgerant (to remove any existing moisture), then you will receive trouble-free service from your existing compressor. If I'm wrong, someone will correct me, I'm certain.

[MisterMan]

Originally Posted by chevydog66

I have a 72 GMC truck with factory A/C. I recently purchase the POA Update kit for R134, drier, and condensor for my truck. Will I be able to use the new R134 in my old original compressor? I know that the R134 operates at higher temperature and pressures. Will the old original compressor be able to handle it?

old stuff has been in there. no matter what, their will be traces... not worth it to fry ur entire system over one old part..... just my opinion, do what u want...

--den

[JimKshortstep4x4]

I have converted three systems which still use the old compressors and have had no problems, (66 SS Impala, 69 El Camino, and 71 C-10). In addition to Tynees very good advise, I would suggest making sure the condenser, fan, shroud, and fan clutch are up to snuff as without good air flow the pressure will increase as the temperature goes up.

JIm

[incoma]

ditto the conversions. swapping the dryer is a good idea to eliminate moisture and freshen the system. I've converted several without doing this and they work ok.

[Bob B.]

The major issues with converting an old R-12c system to R-134A is that the mineral oil used in R-12 systems will not work with R-134A, which needs a synthetic oil. A Fridgidaire A-6 compressor will work fine with R-134A, if it is in good shape and you drain as much oil out of it as possible. The dryer must also be R-134A compatible. The only other issue is that R-134A will permeate R-12 hoses over time. So, if you don't change the hoses, expect to recharge the system from time to time. This is a pretty good site for more specific information:
http://www.ackits.com/

[mrein3]

The advice above is good.

Regarding draining oil from your compressor...
I have read that you should drain it. Then fill it with a measured quantity of the R134a compatible oil, then drain it again. Measure the oil on the way out to make sure you get most of it out. This will "flush" the old oil out of the system.

ALWAYS, ALWAYS, ALWAYS replace the receiver/dryer when you open the system. They are only $20-$30.

ALWAYS, ALWAYS, ALWAYS pull a vacuum for 30 minutes to boil the water out of the system (remember from high school chemistry - when you decrease the pressure, the boiling point of a liquid, in this case water, decreases)

If you poke around on the ackits website you will find instructions on how to adjust your factory POA to work with R134a.

To make a long story short, your old A6 compressor will do just fine with the "new" stuff. If fact it is a better compressor than the later model GM ones. I NEVER replaced an A6 on a car. I've replaced many of the other types. And that was back when the A6 compressor was still more common than the new little one.

[chevydog66]

Thanks for the comments guys. I do have a new radiator, shroud, R134 dryer, and new POA update for R134. So I guess I will try using the original A6 compressor. I have heard that it won't work with the PAG oil. So should I use the PAG oil, or whatever it is called, or mineral oil in the compressor?

[chipflyer]

You want to use Ester oil, (POE) it is compatable with the old mineral oil in the R-12 systems and with PAG oil used with 134. When I did mine a couple years ago I drained my good A-6 (original) compressor and replaced the old mineral oil with Ester oil, turned the compressor by hand, tilted it up, down and turned the pump by hand some more. I drained the oil and did this same thing 3 times then filed the system with the proper amount of oil. Flush your lines, evaporator and condensor but NOT your compressor, expansion, POA or reciever/drier with good old laquer thinner, blow it all out put it together and then pull a vacuum on it for several hours to burn any moisture out of the system. This has worked well for me in the past on several old systems.

Jeff

[Joesjunk]

How cold does the air blow on the converted systems??

[incoma]

My 90 truck blows real cold. I normally have to back if off of the coldest settings after a few minutes. I think my system holds about 2 lbs of coolant. I'm running stock components, with an extra can of PAG in the system. I had a leak a few years ago and lost all of the R12. That's when I replaced a hose and put R134a in the system. I've still got a small leak so every year I put another can or 2 in the system. I'm just lazy.

[SactoJim]

Hope this isn't a stupid question, but what the best way to "pull a vacuum" on the system? Do you have to have any specialty tools?

[Fred T]

You need a vacuum pump and a set of manifold gauges. I recommend having a shop do the vacuum if you don't have the right tools. Pulling the vacuum also does a leak check by letting the system sit for a few minutes and checking the gauges.

[68speedalert]

Follow what Fred & chipflyer say. Don't be too concerned about the mineral oil, The a/c compressor re-builders have found where a little mineral in the compressor makes it last longer than just pag or ester. They also think that unit run on r-12 and converted, will hold up better as well.

I would recommend you vacuum for at least 1 hour, getting as close to 30 inches of vacuum as possible.

Amount of charge equals r-12 capacity times 90% minus .25 pound, as a starting poiont. That is GM's formula.

FWIW, I'm ASE certified in a/c work.

[badpeanut]

Who carries the "POA update kit" and what does it cost?

[chevydog66]

I purchased the POA update valve kit for R134, from Chevy Duty or whoever they are called now, for about $90, I think.

[chipflyer]

How cold does the air blow on the converted systems??

My stock looking converted system will cool between 42-45 depending on the outside temp and whether or not I am in town or out on the highway.

Your stock POA valve can be adjusted to work with 134. It is a very simple mod if you have A/C equipment. Here is link that explains in detail.
http://www.autoacforum.com/messagevi...AR_MSGDBTABLE=

[humbulay]

I borrowed my grandpas 62 chevy truck while i was restoring my 71 c10. the 62 had what looked like a late 60's sears underdash unit it using R12 but had a small leak. One of my mechanic buddies pulled vacuum on it, drained the old lube, switched the r12 filler fitting to a 134a fitting (cost of $2.35), filled her up w 134a, added a can of 134a stop leak w/ lube & it has worked fine for over 4years now!!! and it blows colder than it did with R12!!!

[chevydog66]

Thanks for the replies. I'm going to juice her up with R134a pretty soon.