the AC in my 85 hasn't worked in years, and the last thing to wrap up my current project is a system repair and R12 to R134 AC conversion.

we lost all the R12 freon due to a hose failure (a split hose coming off the back side of the compressor). I have purchased, new ACDelco hose assemblies that are R134 rated. I have also purchased a new accumulator(dryer), and plan to purchase a new GM R4 compressor and orifice tube valve assembly. i'm pretty sure there's bearing issues with the compressor, and a rebuild would be necessary. i'm opting to go with a new GM unit (w/clutch assembly) vs. a rebuild. I will be doing a solvent flush of the evaporator and condenser along with remaining hardware, and for the flush, i'll be using a flush kit from FJC.

per the FSM, the system takes 6 oz. of oil, and from an on-line R12/R134 conversion site, it's recommended PAG150 oil for an R4 compressor system. the system is spec'd at 3 oz. in the evaporator, 2 oz. in the condenser, and 1 oz. in the accumulator. the compressor is not supposed to have any type of sump, and will hold only a residual amount of oil. from yet another site, it said to add several oz. of oil while turning the compressor, and set the compressor on the bench, clutch side down, and let the oil permeate thru the assembly and after several days - then drain off the excess oil. once the system is back together, pull a vacuum on the system per standard procedures, and finish up with approx. 2.3 lbs. of R134 (the R134 fill is supposed to be 85% of the R12 capacity).

so, in a nutshell, that's my game plan. this AC stuff is kind of virgin territory to me. i'm comfortable with the "nuts and bolts" end of things, but unsure about the technical end of the conversion. i'm kind of in information overload on the conversion process, so, for the AC guys, do you see any issues in my thought process, any comments, suggestions, am I out in left field, a better way, or whatever. as a last resort, I may have an AC shop do the final vacuum thing and R134 fill, but not sure at this point.

couple final questions - the low pressure service valve is located at the accumulator - correct (just double checking), and, I read that it's better to install a variable orifice tube assembly vs. a fixed valve - comments on that, and, any benefit to replacing the compressor coolant temp switch and the pressure cycling switch, or is it OK to use the originals. anything else? TIA....

 

Okay, so first off, no one I know that has done a R12 t0 R134 change out, at least by just replacing the r12 with r134a has been happy. And the reason goes something like this; r134a is actually a more efficient refrigerant, BUT it is designed to operate at a higher pressure than r12 and an r12 compressor simply won't develop high enough pressures to allow the r134a to work efficiently.

Then again maybe all this is just so much b.s.; I don't know, but I would really investigate whether the components that you are intending to install are r134a compatible.

One a side note, can any stock corvette r134a systems from later vettes be retro fitted to your car?

 

My 87 has been converted to 134 and it cools just fine. It's using the stock 87 system including the compressor. I've also done R134 conversions on several other cars, including Pontiac Fiero's and a Porsche 928 and 944 and I've been very happy with the cooling output in each case, here in Atlanta, GA. One thing to watch, the total charge, by weight, of R134 is about 15-20% less than a charge of R12 or you run the risk of high side pressures getting too high. A variable orifice tube does seem to help the cooling when you are sitting at idle.

 

my 85 cools just as well as it did when new. That's after buying a conversion kit at Walmart 10 years ago and going at it. Never leaked since

 

Hi

I would recommend ester oil for R12 to R134a conversion if using the old compressor, that oil will work fine with R12 or R134a.

Pag oil is good if you are replacing the hoses, compressor accumulator and using solvent to clean the condenser/ evaporator.
You need to replace the o rings with the green/purple type do not use the black rubber ones.

The original pressure switches are fine, just remember only use 80% of the R134a fill compared to R12 amount. (there is a label on the a/c box in the engine bay)

You can buy 134a screw on fittings on ebay that will fit the high and low side.

good luck

 

Ester oil.

Green "O" rings.

134 works ok in vehicles with electric radiator cooling fans. The poor cooling @ idle issue when using 134 stems from conversions on vehicles with engine driven cooling fans that do not pull enough air past the condenser @ idle RPM.

 

Joe C. I agree with some others here. After the conversion from R12 to R134a, I tend to run the AC on my 88 at the 60 F temp in the daytime during Summer but it cools and is better than no AC at all.

 

Looks like you've done your home work! Yes the accumulator fitting is the low side of the system, and yes you should change the low pressure cut out switch with one that is rated for the operating pressure's of 134a.. now my only Question for you is; is there a more efficient, After market Condenser for your 85, this will keep the Head pressures down and allow the system to Cool a bit better.

 

Why exactly? If it is rebuilt properly, I don't see an issue. OTOH, if you are thinking (stupid) of asking Bob's Bar and Grill and AC Shop to do it, I would be worried. I have been recommended to try Hancock Industries in Abilene, TX a few times and been happy with the results. YMMV.

I have seen mechanics and I myself have put a couple ounces of oil in the compressor, turned it a bit.

As a last resort? Why exactly do you say that? How do you intend to pull a vacuum and hold it for a few minutes? I just did one and had my buddy run it on his shop machine. We did a 15 min vacuum. How exactly do you plan to accomplish that? You suck that good? Also, how do you plan to charge the system? I wouldn't use those crap in a can. I would want a machine that can do all THIS. Can you do that in your garage? If not, I wouldn't. My neighbors do not have this so it is cheaper to get it done at a shop than to pay less today (called cheaper by idiots) and pay more tomorrow. I tend to steer clear of things that are cheap and too good to be true. Leaky AC? Just $20 and you can avoid the shop and fix it yourself. Thanks but I CANNOT afford that.

If it were me (the last moron who owned my car did it), I would NOT do the switch. In spring or fall, it is great. Even my AC instructor told us that while it feels good it doesn't work quite as well in stop and go traffic in the summer. R134A system to R12 is a push. R12 converted to R134A has not worked as well at least in our classroom and on my car.

 

I wasn't able to get the variable orifice tube since the one they sent me didn't fit and I got the standard one out of necessity so I can't say how it works for that case. However, my 91 Firebird was converted to R134A in the middle of a summer and done professionally by a reputable shop. IT WAS NEVER AS GOOD AS BEFORE. Normal operations might take longer to get to temp but under extreme conditions like being baked in the sun, it definitely takes longer. I can't remember why but I had timing for that and it was noticeably longer for a given cabin temp. Since I had to open the door momentarily and some hot air escaped, I would agree it isn't as scientific as I wanted.

 

My 91 F-body has electric fans. It didn't work as well at idle and in stop and go traffic as before the conversion.

 

Amazon has R12 going for $130 and R134A going for $270 in a 30# jug. While R12 costs twice more than R134A on Amazon (just using it as a gauge when it comes to the shop), you are only using a few pounds (less than 3) of the stuff. Why would you think it would be cost effective to rig up something like that to be just as good (assuming you could) when you can pay a few bucks more($13 vs $27 in the example) and leave it be without trying to jury rig up something to work?

 

Stated that it works OK.

If you are not satisfied with the 134 conversion ES12A is colder. A newer style manifold condenser will help.

 

Why? It costs more than R12

 

I did the conversion in my 84, I weighed going back to actual R12 vs 134a and decided 134a was the way to go.

I can get R12 by emailing a waver to some sellers, however it would have cost me about 4x as much as 134a.

And in the end since I had never actually run the ac in my vette, I had noidea if my compressor was any good...

I had a radiator shop rebuild my hoses, and I bought an inexpensive vacuum pump off of ebay (I think I paid $50 for it), I then picked up a new drier from napa for I think about $20-$30, a cheap R12 manifold gauge set and then I went to town.

I used pag 100 oil as recommended by napa by taking a look at one of their conversion kits as I did not want the conversion fittings...

I also bought some of their ac flush, and ran it through the condenser and evaporator, I also pulled the ac compressor and ran the stuff through It as well.
They had two types, one with a pressurized can and a hose, and the other just can you pour in.

I also bought an Oring universal kit from harbor freight (green type), it worked great, lots of options ect. every black Oring swapped out, just make sure you lube them up before assembly or they might get damaged and leak.

End result was a pretty decent cooling ac, It ran every bit as good as my 2003 s10 and my wifes 2007 Saturn AC does.

I also like the freedom of the 134a, while working on the car I don't have to worry much about having to refill the ac again.

and while your at it, replace the ac orphus tube.

For my 84 it was on the evaporator, lower hose connector (part on the firewall).

It also worked out great, while tearing the car down this winter I upgraded the camshaft, not having to worry about loosing expensive refrigerant while moving everything out of the way was fantastic.

 

So? It isn't like you are doing 3000# of the stuff. IIRC, it is under 3 pounds.

Me neither but in my 91 F-body, there was significant difference after the conversion if you want an "apples to apples" comparison.

But how does it run compared to what it WAS? Comparisons should be done as a "before and after" and not "Apples to Oranges" if they are to be meaningful.

I don't follow. I can find a shop, have them suck out the refrigerant and refill it when I am done. How do you think they do this when they are working on a car? Unfortunately, I have R134A but if I were to open the system, I'd still have to have it vacuumed and recharged.

How expensive is R12? On ebay, it is about $30 for a 12 oz can. http://www.ebay.com/itm/Sercon-R12-R...lWefWo&vxp=mtr. Now if you are opening your system every day, I can see $90 going out as an issue. I can't think of the last time I opened up the system other than when something broke in the AC. If I were taking out my heads every week, sure. Still, have a shop recover it. I would think that if you bought recycled instead of virgin R12 it could be cheaper? Just a thought.

 

I always understood that R12 was actually better, and my wife's grandma had an old low mileage Honda from the 80's that spit out fog from the vents like a opening a freezer on a hot summer day...

I had actually planed on going R12 after the reassembly, but I was happy enough with the 134a though out the summer here.

Also my neighbor is a hvac tech, I'm pretty sure if I gave him a 6 pack I could get him to fill it for me (to comply with laws related to R12, another reason why I like the idea of 134a).

 

It's depending on how the system is designed. Our system was designed to work with R12. You shoehorn R134A and you can't expect it to work as well during trying conditions.

 

thanks for the feedback, and thanks for the comment on the low pressure cutout switch.

I just picked up a copy of a retrofit guide from FJC. seems these people have been in the retrofit business for some 20 years. they also commented on the LP cut out switch, and recommended replacement. in their guide, they recommend an ester oil which seems to work on both R12 and R134 systems vs PAG. forum members gerardvg and Churchkey noted the ester oil - . as for the condenser, FJC indicates that if the original condenser is in good condition, replacement may not necessary. I weighed the cost of replacement and opted to keep my original. one further thing I picked up on was the orifice valve assembly. FJC also suggests switching from a stock GM unit which seems to have a .072 diameter orifice to one with a slightly smaller orifice diameter - .067. seems the smaller diameter component has a benefit during idle operation. on another thread on conversion, another member verified this information.

i'm having a better feeling about this conversion. not sure on what route i'm going to go on the vacuum and system charge though. if I do it myself, i'll need to invest in a pump and manifold gauge set, hoses, etc. I may have a lead on borrowing a setup, but then again, I just may farm it out to an AC shop.

 

I tried the variable orifice but although it was supposed to be for my application, it didn't fit so I had to run out and buy a stock sized one. I would get one from GM and keep it on hand just in case.

Why would you buy all the stuff, assemble it and try make it work when you can get it done professionally with a machine that can inject oil for you as needed? Say you do get it right, now what do you do with all that crap you bought? Save it for something in the next 5 years? I got my Vette in 05 (I think), saw the way the PO does his work and didn't trust the conversion so I took out every O-ring (found a few blacks), replace them and had it done. Didn't need to do anything till the compressor crapped out a couple years ago. You save a few bucks but you have a higher risk and a bunch of parts you don't have a use for and it sits.