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#1 |
Registered User
Join Date: Jul 2014
Location: Chico, California
Posts: 941
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I would like to convert the factory AC system in my '72 to R134a so that in the long run it will be easier to service (and because it doesn't work right now). I understand the basics, but I'm learning as I go when it comes to this AC stuff so please explain like I have never heard of these parts. Thanks in advance!
![]() ---- Questions: Could I use the stock controls and evaporator, and change the rest of the system under the hood for R134a - compressor, condenser, fittings, hoses, drier? I found in some research a recommendation to upgrade from the POA valve system to a orifice/accumulator type. I also read something about a switch that cycles the compressor on and off so the evaporator doesn't freeze. Can someone explain this? Do I need a different expansion valve? Is there a kit available for doing all this? Is this a cost-effective way to upgrade the AC system that will also work well? |
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#2 |
Registered User
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Location: colorado springs colorado
Posts: 49
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Re: Converting factory AC to use R134a
through lots of searching on this site i had found a thred where a guy in az did the conversion and used a mix of parts and had got it to where he was able to use 134 and it would stau cool at idle when stuck in az stop and go traffic now if i could only find his post again being that i bought all my ac hard parts today keep looking on here its bound to be somwhere
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#3 |
Senior Member
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Location: Sandown, NH
Posts: 2,819
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Re: Converting factory AC to use R134a
Subscribed
I plan on doing the same and need to know the best way to make it work ! Gary
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Gary 72 SWB 4x4 My 72 SWB Build http://67-72chevytrucks.com/vboard/s...d.php?t=259859 |
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#4 |
Registered User
Join Date: Jun 2010
Location: Upland Ca
Posts: 4,143
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Re: Converting factory AC to use R134a
About 10-12 years ago I took my factory AC truck to my local AC shop were they evacuated the system, changed the fittings, pull a vacuum, and recharged it with the proper oil and 134. Only cost about $100 bucks. Cooled very well until I tore it down for restoration.
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1972 C10 SWB, Air, PS, PB, 350/350THM. Second owner. 1965 Corvette roadster, 44K miles, 327/365 SHP, 4 speed, side exhaust, knockoffs, teak, second owner (bought in 1970), Have ALL numbers matching components. My frame off restoration thread: http://67-72chevytrucks.com/vboard/s...d.php?t=556703 |
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#5 |
Registered User
Join Date: Nov 2014
Location: Austin
Posts: 749
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Re: Converting factory AC to use R134a
Interesting timing on this thread. I purchased a 71 this past Saturday with factory a/c. The a/c is non operable, but all there and seemingly original equipment. It is also obvious that 134a was used as the low side valve is of the 134a type (adapter fitting). My plan is to go back to R12.
I live in Austin, TX where summer time temps reach 100+ very regularly. In my past experience with converting R12 systems to R134a it just doesn't cut it in Austin. The reason is mostly the condenser....R134a is less efficient in eliminating latent heat than R12. Thus you need a large condenser to shed that latent heat from the R134a refrigerant. If you live in cooler climates then a conversion usually performs fine (i.e. Chico, California). Also, I suspect the original factory components are robust enough the handle the higher operating pressure that you get from R134a. The hoses will be thoroughly impregnated with oil and thus probably wont leak out the smaller R134a molecules. The compressors seals may be an issue and I worry about oil contamination. Probably a good idea to have the compressor rebuilt and tell the shop that you plan on converting to R134a. I will disassemble my system and flush all lines, hoses, evaporator, and condenser before switching back to R12. I know it may seem crazy to switch back to R12, but I have a 30# cylinder of R12 sitting in my garage (about 2/3 full) with no vehicle to use it on. And, I am a certified a/c mechanic (got it online many years ago) so I can buy R12 from the auto parts stores. R12 simply works better than R134a. Hope this helps... Edit: Almost forgot...you MUST change out the receiver/drier...oil contamination if you don't. All the other components should work just fine after a thorough flush. And, freezing of the evaporator should be a non issue since the system wont cool as well as with factory R12. So, if it didn't freeze up with R12, it surely wont with R134a. Last edited by Davidf; 03-17-2015 at 10:02 AM. |
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#6 |
Registered User
Join Date: Feb 2012
Location: Smyrna TN
Posts: 1,153
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Re: Converting factory AC to use R134a
I replaced my POA valve with the hi/lo pressure switch, flushed the system, and added the different oil required by 134a. I should have changed my condenser to a high flow as it doesn't cool as good as it should. In hind site I wished I had just had my POA re-calibrated and not gone with the switch. If you call vintage air I'm sure they could give some good advice on the necessary steps.
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1971 Longbed BB Cheyenne Super 1972 Longbed SB Cheyenne Super 1972 Longbed Highlander Custom Deluxe 1975 K5 4x4 full convertible Build Thread http://67-72chevytrucks.com/vboard/s...d.php?t=645165 Greg Smyrna TN |
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#7 | |
Registered User
Join Date: Jul 2014
Location: Chico, California
Posts: 941
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Re: Converting factory AC to use R134a
Quote:
Another suggestion I found was to add an electric fan to the condenser. What would turn that on/off? |
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#8 |
Registered User
Join Date: Feb 2012
Location: Smyrna TN
Posts: 1,153
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Re: Converting factory AC to use R134a
David you are correct on the receiver dryer. Any time the lines are open I would replace the receiver dryer, its only about $20 and can prevent hundreds of dollars and frustration by skipping that step.
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1971 Longbed BB Cheyenne Super 1972 Longbed SB Cheyenne Super 1972 Longbed Highlander Custom Deluxe 1975 K5 4x4 full convertible Build Thread http://67-72chevytrucks.com/vboard/s...d.php?t=645165 Greg Smyrna TN |
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#9 |
Registered User
![]() Join Date: Mar 2014
Location: Luray, VA
Posts: 73
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Re: Converting factory AC to use R134a
I've done this switch on several vehicles. The key steps are changing the charging fittings, changing the oil, thorough evacuation, and recharge. It is a good idea to change the receiver dryer which is a cheap part. A reputable shop can do this work for a very modest price. Forget anyone who wants to mess with the compressor, valves, hoses, seals, etc. That's just a way for a shop to take money out of your pocket.
As to cooling performance, I've checked vent output temperature with an AC thermometer. It's very close if not identical.
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Bill Shenandoah Valley of Va 1972 GMC 2500 Sierra Grande 402, Custom Camper Package |
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#10 | |
Registered User
Join Date: Nov 2014
Location: Austin
Posts: 749
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Re: Converting factory AC to use R134a
Quote:
As for the receiver/drier, most think if you open the system you MUST change the receiver/drier. I don't adhere to that camp. If you open the system, you can reuse the receiver/drier because when you evacuate the system, you boil the moisture out of the receiver/drier. That is why you leave the vacuum pump running for at least 30 minutes. Longer in cooler weather. But, if you change oil/refrigerant types, I say you MUST change the receiver/drier. But, changing the receiver/drier is never a bad idea, especially if they are old. |
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#11 | |
Registered User
Join Date: Aug 2006
Location: Redmond, WA
Posts: 6,332
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Re: Converting factory AC to use R134a
Quote:
I have a couple of questions if someone could address them: - Would an AC shop need to pull apart under my dash, or in the heater core area that would require pulling a fender? I have brand new paint. It looks like the inboard section of the underhood HVAC box comes off. But are all the parts in there? - When I buy a new pump and dryer from LMC, as I did, it has some oil in it. Would that be the old style or new? I poured it out but did not flush it. Just a reminder - this thread is (or was supposed to be) about converting factory air, not replacing it with aftermarket serpentine chrome modern pumps or Vintage air.
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1970 GMC Sierra Grande Custom Camper - Built, not Bought 1969 Pontiac 2+2 427/390 4-speed Coupe 1969 Pontiac 2+2 427/390 4-speed Convertible |
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#12 |
Old member
Join Date: Jan 2002
Location: Liberty, & Garden City S.C. , U.S.
Posts: 19,936
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Re: Converting factory AC to use R134a
Well if you would have look at the page you would have found they have correct factory parts to swap it over to 134A. Sorry I tried helping you out by giving you a company that knows these systems in and outs and are not guy's guessing at this stuff.
Sorry! ![]()
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1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 ![]() Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs. |
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#13 | |
Registered User
Join Date: Aug 2006
Location: Redmond, WA
Posts: 6,332
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Re: Converting factory AC to use R134a
Quote:
And fix your font already. No one wants to read your bold red text. Otherwise, you're a scholar and a gentleman and usually a source of helpful information. But that font just makes me angry.
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1970 GMC Sierra Grande Custom Camper - Built, not Bought 1969 Pontiac 2+2 427/390 4-speed Coupe 1969 Pontiac 2+2 427/390 4-speed Convertible |
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#14 |
Registered User
Join Date: Apr 2014
Location: frisco tx
Posts: 99
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Re: Converting factory AC to use R134a
This guy gets rave reviews for refurbishing 67-72 sytems, but he's on facebook, no web page.
https://www.facebook.com/factoryautoair |
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#15 |
Registered User
Join Date: Feb 2012
Location: Smyrna TN
Posts: 1,153
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Re: Converting factory AC to use R134a
Jim I like the look of the POA better and I've not been able to keep the compressor from cycling more than I like at highway speeds. I've done the fan on the condenser and wired it to the power lead to the compressor so it only runs with the a/c on, and it does help a little. Its off right now but I'm either going to put the fan back on or change the condenser. Bill I'm glad you've had good success with converting your's over. Other folks I know and trust have said the same thing. More often than not I've been advised that the increased pressure does typically require changing the condenser.
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1971 Longbed BB Cheyenne Super 1972 Longbed SB Cheyenne Super 1972 Longbed Highlander Custom Deluxe 1975 K5 4x4 full convertible Build Thread http://67-72chevytrucks.com/vboard/s...d.php?t=645165 Greg Smyrna TN |
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#16 |
Registered User
Join Date: Oct 2010
Location: Ocean Springs, MS
Posts: 1,746
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Re: Converting factory AC to use R134a
An 87 evaporator will fit in the original box.
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Gary 1971 Chevrolet C/10 1951 GMC 100 1977 GMC C15 1955 Chevrolet 3100 |
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#17 |
Registered User
Join Date: May 2011
Location: Fort Pierce, FL
Posts: 430
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Re: Converting factory AC to use R134a
Does anyone make a parallel flow condenser for our trucks? I haven't checked in a couple years.
I got one for my 72 Cutlass and it made a MAJOR improvement in cooling. Also, had the POA recalibrated for 134A and I get 30-35 degree air from the vents with little loss at traffic lights. Basically you flush out the system, replace all the O-rings with ones for 134A, add a new filter dryer, evacuate the system and recharge with 134A at 75-85% of the R12 amount. Don't pay attention to bubbles in the sight glass, because it doesn't work the same with 134A. I used my existing hoses, that were impregnated with the old R12 oil and have had no leaks. I also bought a Haynes A/C Manual, that helped me understand the whole A/C theory. |
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#18 |
Registered User
Join Date: Nov 2014
Location: Austin
Posts: 749
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Re: Converting factory AC to use R134a
For the same reason you replace all the O-rings to R134a compatible material is the same reason I worry about the front shaft seal on the compressor. It would be wise to replace the compressor seal as well. And, the mineral oil must be thoroughly removed from the compressor and replaced with PAG/Ester oil. Mineral oil (R12) and PAG/Ester oil (R134a) do not mix. Mineral oil and R134a do not mix. So, any left over mineral oil will find the low point in the system and say there. That is usually the condenser and thus condenser efficiency can be slightly compromised.
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#19 |
Senior Member
![]() Join Date: May 2003
Location: Sandown, NH
Posts: 2,819
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Re: Converting factory AC to use R134a
Lots of good info here !!!
OK, I'm an HVAC Tech but just don't have much experience with automotive A/C. I did some research on other forums and there's more than one way to do the conversion. The following is the approach I'm going to take partly because I'm doing a ground up resto-mod and I have a new sanden compressor. * New Sanden Compressor * New condenser coil ( Parallel flow for R134A ) * New drier * New custom lines set * Adjust the original POA valve to 26.5 PSI * I already have electric fans with a controler that brings on the fans for the A/C. * Replace all o-rings * Flush the system * Add the proper amount of PAG oil * Re-use the remainder of the original system. * Evacuate and charge the system to 75-85% of the original charge At least this is what I'm thinking at this point. Gary
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Gary 72 SWB 4x4 My 72 SWB Build http://67-72chevytrucks.com/vboard/s...d.php?t=259859 Last edited by CUSTOM/10; 03-17-2015 at 01:03 PM. |
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#20 |
Registered User
Join Date: Nov 2014
Location: Austin
Posts: 749
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Re: Converting factory AC to use R134a
You plan is sound. The new condenser matched to R134a refrigerant will make all the difference. I installed a Old Air Products system in my '52 truck (all matched to R134a) that utilized a Sanden compressor, electric condenser fan and it will freeze you out. Good luck.
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#21 |
Registered User
Join Date: Feb 2000
Location: Center City, MN, USA
Posts: 3,254
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Re: Converting factory AC to use R134a
I added AC to my non-AC truck.
I never was a certified AC mechanic but I did LOTS of AC service in a small, non-chain shop while paying my own way through college. Everything I learned about automotive AC was on the job training. Since I have WAY more time than money, I chose to put in all stock AC parts, and adjust the stock POA to work with R134a. I'm approaching my 5th summer running R134a with everything else stock with ZERO problems. Other than the stupid o-ring on the schrader valve on the POA leaks. I did a write-up on it here: http://67-72chevytrucks.com/vboard/s...d.php?t=478564 I hope this helps.
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'70 cab, '71 chassis, 383, TH350, NP205. '71 Malibu convertible '72 Malibu hard top Center City, MN |
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#22 |
Moderator
![]() Join Date: May 2007
Location: Southern Cal
Posts: 20,005
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Re: Converting factory AC to use R134a
134 will leak out of the front seal on a rebuilt stock (A6) compressor eventually. I went through four of them. If you live where it gets HOT (and I don't mean 80) r134 will not work well in a factory system with the stock condensor. I will only use R12 on a factory system.
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1972 C/10 Cheyenne Super SWB. Restored, loaded, slammed. 1968 C/10 50th Anniversary LWB. Unrestored, stock, daily driver/work truck. RIP ElJay RIP 67ChevyRedneck RIP Grumpy Old Man |
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#23 |
Senior Member
![]() Join Date: May 2003
Location: Sandown, NH
Posts: 2,819
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Re: Converting factory AC to use R134a
How much oil should be put into the system once it has been flushed of the old oil ?
Gary
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Gary 72 SWB 4x4 My 72 SWB Build http://67-72chevytrucks.com/vboard/s...d.php?t=259859 |
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#24 | |
Registered User
Join Date: Jul 2014
Location: Chico, California
Posts: 941
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Re: Converting factory AC to use R134a
I got an email from John at Old Air Products. He said this would convert the truck to a fully functioning R134a setup, and it all bolts in. What do you AC experts think about doing it this way?
Quote:
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#25 |
Old member
Join Date: Jan 2002
Location: Liberty, & Garden City S.C. , U.S.
Posts: 19,936
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I've been running 134a in mine for as long as I can remember and no problems. I bought the kit when I did it from Classic air. I had the old parts that I took off another truck first but the old A-6 compressors wouldn't hold up. I since have swapped a 6.0 in it and it runs great now to. I swapped condensor acumalator did away with the drier, and put the orfice tube in the bottom line. I bought the hose kit and brackets along with sanderson compressor and ran it for several years before I did the LS swap.
![]() http://www.classicautoair.com/GM_OEM_Parts_Engine.html ![]()
__________________
1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 ![]() Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs. |
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134a, a/c, air conditioning, r134, r134a |
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