AC Questions

mikester

Royal Smart Person
Mar 10, 2010
2,004
113
Small town NY
Im finally getting to one of the last things that I had to finish on the wagon. The AC system. The original AC box was damaged when I got the car so I grabbed a really clean one out of an 87 Cutlass at the local yard. Took it completely apart and cleaned everything that was there. New heater core and evaporator. New accumulator and condenser. I found a good liquid line (I think thats what its called) from a Regal at a different yard and it looks like its going to work. I have a line from a Cutlass sedan and for some reason its at least 3 inches too long. I found that strange since Im using a condenser from a mid 80s Cutlass.
The last major part I needed was the refrigerant hose and I got that on Friday. Bought the part number that someone gave me in my thread last week. Turns out that the line to the condenser was still too long by at least 6" so I had that modified today. The hardest thing was finding a shop that did bead lock crimps. Lucky for me a small radiator/AC repair shop about 40 minutes from my house was able to do it for me.
Tomorrow Im going to try to get it all together. That leads me to this question. What else do I need ? I know I have to get an orifice tube. The guy at the shop said he could put it in when I bring it there to charge the system.
Im assuming I have to put oil in the compressor ? I called the dealer where I bought the crate motor. They only have R-134 PAG 46 oil in canisters but I was able to get a small bottle at the local auto parts. The parts guy at the Chevy dealer had no idea how much to put it. Anyone know ?
The first dealer I called which is only 12 miles away couldnt tell me either. The best part was their parts guy telling me theres no such thing as a 350/330HO crate motor. LMAO
 
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69hurstolds

Geezer
Supporting Member
Jan 2, 2006
5,272
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Light reading from the GM service bulletins:

#33-12-26: RETROFITTING R-12 VEHICLES TO R-134A (INFORMATIONAL) - (May 10, 1997)
---------------------------------------------------------------------- REVISION 01/18/94

THIS BULLETIN HAS BEEN REVISED TO PROVIDE ADDITIONAL INFORMATION IN THE "RESIDUAL MINERAL OIL" SECTION. ----------------------------------------------------------------------

SUBJECT: RETROFITTING R-12 VEHICLES TO R-134A

MODELS: 1994 AND PRIOR YEARS, PASSENGER CARS AND TRUCKS WITH R-12 A/C SYSTEMS

THERE HAS BEEN A GREAT DEAL OF INFORMATION PRESENTED BY THE MEDIA REGARDING THE NEED TO RETROFIT VEHICLES PRODUCED WITH R-12, TO A SUBSTITUTE REFRIGERANT. THIS BULLETIN WILL OUTLINE GM'S POSITION AND FUTURE PLANS ON THIS SUBJECT.

**MOST IMPORTANT, THERE IS CURRENTLY NO REQUIREMENT TO RETROFIT ANY R-12 VEHICLE. VEHICLES BUILT WITH R-12 CAN BE SERVICED WITH R-12, AS LONG AS THE REFRIGERANT IS AVAILABLE.** AT SOME POINT IN TIME, R-12 MAY BECOME EITHER TOO SCARCE OR TOO EXPENSIVE TO ECONOMICALLY JUSTIFY SERVICE ON SOME VEHICLES WITH R-12. BY THAT TIME, GM WILL PROVIDE YOU WITH INSTRUCTIONS ON RETROFITTING THOSE VEHICLES FROM R-12 TO R-134A.

GM VEHICLE DIVISIONS, PLATFORMS, AND COMPONENT SUPPLIERS HAVE BEEN ACTIVELY WORKING ON THE DETAILS OF RETROFITTING R-12 VEHICLES. AN ENORMOUS AMOUNT OF WORK IS REQUIRED TO DETERMINE HOW HUNDREDS OF VEHICLE MODELS CAN BE SATISFACTORILY RETROFITTED. ADDITIONAL INFORMATION WILL BE PROVIDED AS IT BECOMES AVAILABLE.

THE FOLLOWING ITEMS CONTAIN IMPORTANT TECHNICAL INFORMATION THAT SHOULD ANSWER MANY OF THE QUESTIONS, AND CORRECT SOME MISCONCEPTIONS REPORTED IN THE MEDIA.

SUBSTITUTE REFRIGERANTS

R-134A IS THE **ONLY** APPROVED SUBSTITUTE REFRIGERANT THAT GM RECOMMENDS AND IT SHOULD ONLY BE USED IF A COMPLETE RETROFIT PROCEDURE HAS BEEN PERFORMED. **NONE OF THE OTHER REFRIGERANTS CURRENTLY BEING MARKETED AS REPLACEMENT OR DROP-IN SUBSTITUTES FOR R-12 ARE APPROVED FOR USE IN GM VEHICLES.**

R-12 AND R-134A ARE NOT INTERCHANGEABLE. R-134A CANNOT BE ADDED TO FILL A LOW R-12 SYSTEM. THE COMBINATION OF THE TWO MATERIALS CAN CAUSE HIGH SYSTEM PRESSURES, WHICH COULD CAUSE DAMAGE TO THE SYSTEM.

RETROFITTING AN R-12 VEHICLE TO R-134A REQUIRES CAREFUL PREPARATION TO INSURE THAT NEITHER THE VEHICLE NOR THE A/C SERVICE EQUIPMENT HAS BECOME CONTAMINATED.

RESIDUAL MINERAL OIL

THE CONCERN THAT MINERAL OIL IS CHEMICALLY INCOMPATIBLE WITH R-134A AND/OR PAG LUBRICANT HAS BEEN PROVEN TO BE UNTRUE. A NORMAL CHARGE OF MINERAL OIL LEFT IN THE A/C SYSTEM AFTER A RETROFIT TO R-134A WILL NOT DAMAGE THE SYSTEM. MINERAL OIL, HOWEVER, DOES NOT MIX WELL WITH R- 134A, AND WILL NOT PROVIDE ADEQUATE LUBRICATION. TESTS ON BOTH THE ORIFICE TUBE AND TXV SYSTEMS SHOW THAT THE MINERAL OIL PARKS IN PLACES SUCH AS THE ACCUMULATOR, AND DOES NOT APPRECIABLY AFFECT PERFORMANCE OR DAMAGE THE SYSTEM. THE RETROFIT SERVICE BULLETIN WILL SPECIFY THE CORRECT OIL TO BE USED. IT IS IMPORTANT THAT THIS OIL RECOMMENDATION BE FOLLOWED CAREFULLY.

RESIDUAL R-12

RESIDUAL R-12 LEFT IN A SYSTEM, DUE TO IMPROPER RETROFIT SERVICE PROCEDURES, MAY RESULT IN SYSTEM DAMAGE UNLESS THE RESIDUAL R-12 IS KEPT BELOW THE 2 PERCENT LIMIT SPECIFIED BY THE SOCIETY OF AUTOMOTIVE ENGINEERING'S SPECIFICATION J-1661. NEW SERVICE METHODS ARE BEING DEVELOPED TO MINIMIZE THE LEVEL OF R-12 REMAINING IN THE A/C SYSTEM AFTER THE RETROFIT PROCEDURE IS COMPLETED. FOLLOWING THESE NEW PROCEDURES WILL BE CRITICAL TO INSURE THAT THE ABOVE LIMITS ARE MET.

SYSTEM FLUSHING

R-11, A MATERIAL COMMONLY USED AS AN A/C SYSTEM FLUSHING SOLVENT, HAS BEEN FOUND TO BE CHEMICALLY INCOMPATIBLE WITH PAG LUBRICANT. TECHNICIANS SHOULD BE AWARE THAT RESIDUAL R-11 REMAINING IN AN R-12 SYSTEM WILL BE VERY DAMAGING IF THE VEHICLE IS RETROFITTED TO R-134A LATER IN ITS LIFE. FOR MANY YEARS GM HAS RECOMMENDED THE USE OF IN-LINE FILTERS AS AN ALTERNATIVE TO SYSTEM FLUSHING.

**SYSTEM FLUSHING, USING EITHER R-11 OR ANY OTHER FLUSHING MATERIAL, IS NOT APPROVED BY GM FOR ANY A/C SYSTEM.**

DESICCANT PROTECTION

IT HAS BEEN REPORTED THAT THE DESICCANT (MOISTURE ABSORPTION MATERIAL) USED IN 1992 AND OLDER R-12 A/C SYSTEMS IS INCOMPATIBLE WITH R-134A AND PAG OIL. THE OLDER DESICCANT WAS DESIGNED SPECIFICALLY FOR R-12 SYSTEMS, BUT TESTING HAS SHOWN THAT IT IS **NOT** NECESSARY TO REPLACE THE OLDER DESICCANT JUST BECAUSE THE VEHICLE IS BEING RETROFITTED TO R-134A. 1993 AND NEWER GM VEHICLES USE DESICCANT DESIGNED TO BE COMPATIBLE WITH BOTH R-12 AND R-134A SYSTEMS.

THE AMOUNT OF DESICCANT USED IN MOST GM VEHICLES IS DESIGNED TO LAST FOR AT LEAST SEVEN YEARS. TO HELP MAINTAIN ADEQUATE PROTECTION FOR VEHICLES THAT MUST BE RETROFITTED, IT IS RECOMMENDED THAT THE ACCUMULATOR/DRYER, WHICH CONTAINS THE DESICCANT, BE REPLACED IF THE VEHICLE IS MORE THAN FIVE YEARS OLD.

"O" RINGS

WHILE CONTINUING TO SERVICE WITH R-12, BE SURE TO USE "O" RINGS AND SEAL MATERIALS WHICH ARE COMPATIBLE WITH R-134A AND PAG OIL. THIS PRACTICE WILL ELIMINATE CONCERN IN CASE THE VEHICLE REQUIRES RETROFITTING LATER IN ITS LIFE. ALL "O" RINGS AND SEAL MATERIALS AVAILABLE FROM GMSPO ARE COMPATIBLE WITH R-134A SYSTEMS.

RETROFITTED SYSTEM PERFORMANCE

CURRENTLY, IT APPEARS THAT FOR MOST GM VEHICLES, THE RETROFIT PROCEDURE WILL REQUIRE MINIMAL CHANGES TO THE EXISTING SYSTEM. SOME VEHICLES MAY NEED ADDITIONAL PARTS AND/OR PROCEDURES TO PROVIDE ACCEPTABLE PERFORMANCE AND/OR DURABILITY. OUR TESTING HAS SHOWN THAT VEHICLES THAT HAVE UNDERGONE RECOMMENDED RETROFIT PROCEDURES WILL, IN MOST CLIMATIC CONDITIONS, BE MINIMALLY AFFECTED IN TERMS OF A/C PERFORMANCE.

SERVICE POLICY

BASIC SERVICE POLICY IS AS FOLLOWS:

DURING WARRANTY - IF AN R-12 PRODUCED VEHICLE A/C SYSTEM MUST BE REPAIRED OR RECHARGED UNDER WARRANTY, REPAIRS WILL BE COMPLETED USING R-12. IF R-12 IS UNAVAILABLE OR UNAFFORDABLE, GM WILL NOTIFY THE DEALER BODY AND WILL PAY FOR THE WARRANTY REPAIR AND THE RETROFIT TO R-134A.

NOTE: IF A CUSTOMER REQUESTS THAT AN IN-WARRANTY VEHICLE BE CONVERTED TO R-134A, AND THE R-12 SYSTEM IS FUNCTIONING PROPERLY, THE CUSTOMER WILL BE EXPECTED TO PAY FOR THE RETROFIT.

OUT OF WARRANTY - THE COST OF THE CONVERSION WILL BE THE RESPONSIBILITY OF THE CUSTOMER.

FIGURES: 0

GENERAL MOTORS BULLETINS ARE INTENDED FOR USE BY PROFESSIONAL TECHNICIANS, NOT A "DO-IT-YOURSELFER". THEY ARE WRITTEN TO INFORM THOSE TECHNICIANS OF CONDITIONS THAT MAY OCCUR ON SOME VEHICLES, OR TO PROVIDE INFORMATION THAT COULD ASSIST IN THE PROPER SERVICE OF A VEHICLE. PROPERLY TRAINED TECHNICIANS HAVE THE EQUIPMENT, TOOLS, SAFETY INSTRUCTIONS AND KNOW-HOW TO DO A JOB PROPERLY AND SAFELY. IF A CONDITION IS DESCRIBED, DO NOT ASSUME THAT THE BULLETIN APPLIES TO YOUR VEHICLE, OR THAT YOUR VEHICLE WILL HAVE THAT CONDITION. SEE A GENERAL MOTORS DEALER SERVICING YOUR BRAND OF GENERAL MOTORS VEHICLE FOR INFORMATION ON WHETHER YOUR VEHICLE MAY BENEFIT FROM THE INFORMATION.

COPYRIGHT 1993 GENERAL MOTORS CORPORATION. ALL RIGHTS RESERVED.

GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.

WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION
 

69hurstolds

Geezer
Supporting Member
Jan 2, 2006
5,272
113
Some random thoughts since I haven't finished my first cup of coffee yet.

With all that, I've seen stickers on converted systems that said around 6 oz. of PAG. That's the reason they put them on there. Which is typical with what it would be regardless. Whenever I do it, I spread the oil around when assembling the system for R12, I'd do it for 134 as well. 1 oz everywhere (condenser, evaporator, hoses [if new]), and the 2 oz in the accumulator and 2 oz in the compressor). I mean, the only thing you're really changing is the refrigerant, so the oil system should be the same needs, IMO. The point is, if you're running an R4 compressor, your oil needs should be approximately the same. Depending on how you're installing 134, check to see if there's any PAG oil already in it (small cans for example). If there is, you may overcharge the oil which means less 134, meaning less cooling if too much oil is added.

Note that 134a takes about 80-85% of whatever R12 amount is needed. On G-body, it's specified as 3.25 lbs of R12. Thus, 2.6 - 2.76 lbs of 134a. If you change to a different type compressor, this may change a bit. I don't know.

Personally, I would use Ester oil myself. It's compatible with either R12 or 134. PAG is not compatible with R12 at all.

I also would suggest perhaps adding a little more oil, maybe an extra ounce, if you put new hoses or other parts on, to make up for a little of the "losses". Maybe I overthink things, but a tad more oil is better than not having enough. You don't want too much, though.

You don't have to do this, but I would put a new accumulator tank on if changing over. The "sock"-like rag material inside absorbs oil, and it is likely mineral oil soaked from the original. And PAG and mineral oil don't mix. It may not matter, but I don't like the idea of using an old accumulator "sock". And 20-30 bucks or so isn't a bank breaker, so...

You do NOT require a variable orifice. There are plenty of places that sell them (cost more) that say you have to have one, but I think it's because they make more money. An original style new orifice tube will work. Variable orifices are called "variable" because it also describes their performance capability results- variable. Some people think they work great, others, not so much.

There's also the claims of needing 134 "barrier" hoses vs. R12 hoses. I don't know for sure if the hoses leak through due to 134 molecules being smaller or not. They may. If your hoses are old as hell, maybe a new set of hoses wouldn't be so bad anyway. Any local A/C shop (full service shop) should be able to make barrier hoses for you if needed. Take your old fittings in, and they can redo them. If going that route, I'd get a 134 stepped mounting pad to the compressor adapted in so you get the right fitting for the compressor needed.

Consider, if you haven't already, a 134a compressor. Newer R4 compressors are made for 134a's higher pressures. They usually have the stepped hose fittings on the back of the unit to help ID them by style. Makes it a PITA if you're using it with your old R12 fitting, however.

There are the hi/lo pressure adapter fittings that usually come with a conversion kit that need to be on there for your 134 stuff. Don't forget those. The 134 gages are supposed to use a slightly different fitting than R12. Don't use R12 gages to monitor the system.

Oh, more random thoughts- if you're using the "original" style condenser with the continuous loop flow, it's good for R12 but not quite as good for 134. The "newer" condensers with the parallel flow is better for 134 (technically it's better anyway for either). Not absolutely needed, but 134 does have the capability of removing more heat than R12, but the components need to matched accordingly. So an old-style R12 condenser won't transfer as much heat out of the system, thus it's not going to be as good picking up that heat from the evaporator.
 

mikester

Royal Smart Person
Thread starter
Mar 10, 2010
2,004
113
Small town NY
Are new condensers available? I remember seeing a lot of people having trouble sourcing the
I bought mine last year right before the shortage. Two from rockauto came damaged. Pretty much trash. I posted photos of the second one.
I wound up getting one from autozone or advanceauto and it was perfect when it got here.
 
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69hurstolds

Geezer
Supporting Member
Jan 2, 2006
5,272
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Are new condensers available? I remember seeing a lot of people having trouble sourcing them.
I have no idea. I have an NOS R12 one waiting in the wings, but no more "newer" cross flows.

Also, the cross flow style seems thinner where the rubber isolator bits sit. IIRC, you can bend in the isolator clamps a bit to make up for that, but if not, some sort of shimming with rubber strips or something may be necessary.
 

melloelky

Comic Book Super Hero
Oct 22, 2017
2,957
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mass
that compressor should have oil in it.in the past I've drained it out,noted how much was in it,put it back in and used that to establish how much total to put in when charging the system..yeah it's kinda odd but..
 
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