R-12 to R-134a conversion

lesbrown · Posted: Fri Apr 04, 2003 3:21 pm Post subject: R-12 to R-134a conversion

I am planning to convert the system on my 70 SS to R-134a. What experience have you had doing this? Any seal or rubber part problems?
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Thanks,
Les Brown
70 SS 396/350 El Camino

acauth1 · Posted: Fri Apr 04, 2003 6:01 pm Post subject:

Assuming the system already works and you are considering converting it as an alternative to the rising cost of R-12, all you would need to do is flush the system of any remaining mineral oil. Replace the drier, 134a install service port adapters, a high pressure cut off switch, add 8 oz of ester oil, and evacuate and recharge the system with 48 oz of 134a.
If you are questioning the integrity of any hoses or oil rings, you should replace them.

jiffyken · Posted: Thu May 08, 2003 8:37 am Post subject: ac

The only problem I have had with the r-134 is that it doesn't blow as cold. not a huge difference but there is one. I have done the conversion twice though. A few degree's warmer is worth not spending the extra money on r-12. And no matter what you do never put that generic freeze 12 in your car for the saftey of you and others. (never liked the idea of propane in my car). Twisted Evil

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"2fst4uraz" 79 caballero

ElkyPete · Posted: Wed May 14, 2003 5:37 am Post subject:

There probably are some things that you can do to correct the differences in the temp between the 134 and the 12. I agree that the 12 was or seemed much colder. However both my 93 Silverado and our 98 Lumina ac systems work really well, except at WOT or past say 80 Mph. I think that is a shut off situation when at high RPMs to possibly protect the AC compressor but then "acauth1" could answer that better than I can because he does that for a living, as I understand it.

Pulling apart the 80's AC box during the restoration I noticed that there were very little differences in it and the 76. However I could never get that POA valve to act right with 134 (on the 76) so I replaced that junk with a conversion to what the 80's AC was. It works far better.

I think that with the new 134 it is hotter after compression so that the newer cars Condensers have a more sophisticated Condenser that helps cool off the Freon more efficiently. If that is correct then you could possibly find a Condenser from a newer car in a bone yard and use that.

I haven't tried it but I think I remember going through all this when trying to get the 76's AC working. I ran into an article that showed the inside cut away of the 134s' Condenser and there are bigger tubes, with some type of small heat sinks built into the inside to better remove the heat.

The 80 has a much simpler system. Gone is the POA that really didn't work well even with R-12. I think that was to "keep the system from Freezing." From the looks of it on the 80 they decided that was not going to be a problem and just didn't use it and went straight into an expansion valve. No cycling on and off no un-necessary thermal couple device and in addition they added a screen around the expansion valve so that some of the foreign objects and debris in the system was trapped. It keeps it from interfering with the work the expansion valve does. That is just my understanding of the system. I don't do that for a living so I am prone to being wrong on things like that.
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