[77sonic]

Anyone done this? Are parts available?

1967 Chevelle with dealer installed unit.

Thanks

 

[200170]

You would have to change all the o rings to be able to use R134 but not sure how well it would work. Usually most adjust the POA valve and even install a parallel condenser but it should work OK I would think but likely not as well as R12. I myself used R12A in place of my R12 (factory AC) in both my cars as a test but it works so well I may not change it to R12 as I planned. It is illegal to mix with R12 or R134 in the USA but many countries like Germany and Canada have been using it solo. But keep that in mind it is flammable but so isn't the newest R1234 coming out now. If I were you I might just change all the seals and buy a couple cans of R12 on ebay. Do you know how much it holds.

 

[SSuper Dave]

Had a '60's era Montgomery Wards underdash unit in a '68 Chevelle a number of years back, I changed the dryer, pulled a hard vacuum on it and charge with R134A, and it spit ice cubes at me. No recalibration needed, but had to adjust the charge volume to allow for the R134A. I drove it that way for a couple of years without issue.

 

[77sonic]

Had a '60's era Montgomery Wards underdash unit in a '68 Chevelle a number of years back, I changed the dryer, pulled a hard vacuum on it and charge with R134A, and it spit ice cubes at me. No recalibration needed, but had to adjust the charge volume to allow for the R134A. I drove it that way for a couple of years without issue.

Interesting! A friend has been wanting to get his A/C working better in his super low mile, mostly original 67. Thanks for the food for thought.

 

[200170]

Had a '60's era Montgomery Wards underdash unit in a '68 Chevelle a number of years back, I changed the dryer, pulled a hard vacuum on it and charge with R134A, and it spit ice cubes at me. No recalibration needed, but had to adjust the charge volume to allow for the R134A. I drove it that way for a couple of years without issue.

It is my understanding that R134A and the required oil will eat the old black rubber orings used with R12. Every Ac that is upgraded to r134 requires new o ring seals to be installed as well as the schrader valve designed to fit the R134 fittings. Maybe the old Montgomery used green Teflon seals.

 

[SSuper Dave]

Bill, ideally you are correct. But the time needed for this to happen is quite long. I've converted probably a dozen a/c systems, using a mix of old and new hoses without issue. My '68 Caprice has been converted for 10 years, and just last year I had to evac and recharge it due to being a bit low. All hose sold now is barrier hose, and I've done a couple of under dash units with all new components, and used barrier hose with green o-rings and R134A.
Oddly enough, I am now going the other way on a '71 GMC Sprint that's using R134a with a recalibrated POA valve. I have 30# of R12, and I am going to change the dryer and adjust the POA and run the R12 in it. No matter how well you convert an old one, it never cools quite as well as R12. My Caprice, with a parallel flow condenser and recalibrated POA, will cool to 40 degrees a the center vent.The last R12 car I had was 35 degrees. Here in Houston, with triple digit temps and humidity, you need every degree of cooling that you can get!

 

[200170]

Bill, ideally you are correct. But the time needed for this to happen is quite long. I've converted probably a dozen a/c systems, using a mix of old and new hoses without issue. My '68 Caprice has been converted for 10 years, and just last year I had to evac and recharge it due to being a bit low. All hose sold now is barrier hose, and I've done a couple of under dash units with all new components, and used barrier hose with green o-rings and R134A.
Oddly enough, I am now going the other way on a '71 GMC Sprint that's using R134a with a recalibrated POA valve. I have 30# of R12, and I am going to change the dryer and adjust the POA and run the R12 in it. No matter how well you convert an old one, it never cools quite as well as R12. My Caprice, with a parallel flow condenser and recalibrated POA, will cool to 40 degrees a the center vent.The last R12 car I had was 35 degrees. Here in Houston, with triple digit temps and humidity, you need every degree of cooling that you can get!

Actually Dave I changed all hoses to barrier and all seals to green Teflon, replaced the condenser, evaporator, dryer and had my POA valve rebuilt on my 68 Chevelle. My wife’s 71 Camaro SS just a couple lines,seals and new dryer. Amazing both compressors were solid. I was not planning to convert to R134a or the newest R1234 but I setup my systems to be able to use both minus the adjustments for the POA valves to use R134A. Not sure about R1234. However I did a lot of reading with the use of R12a which is a replacement refrigerant and can be mixed with either refrig and can use either oil. However in the USA it’s illegal to mix and since my systems were basically brand new I used a pure R12a coolant. Funny R12A works better then either and is much cheaper and more efficient and almost doesn’t even affect the idle when the compressor kicks in. Since both systems were so old I figured I would load the system with R12a to make sure it holds pressure which it did over the winter. Mid vent temp at 1500 rpm is 35f degrees at 75 degrees ambient as tested today with the Camaro. Murphy is still down awaiting a new head but last year it tested about the same. Myself I hate doing anything twice and usually follow the expert recommendations so it doesn’t bite me in the ass later. I can say that R12A does cool better than either coolant of the past so I may just leave both as they are today. Why mess with what works if it cools better then either however there is a safety factor to consider but the new R1234 has the same risk safety wise and cars today used that. However if I do change it will be for R12 and not R134A. Sorry for the long story. I look at it this way, there is always more then one way to skin a cat. Enjoy the weekend.