AC help- R12 to 134A

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jcain226

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Hello everyone!

I have an 88 GMC C-1500 that I am fixing up after it sat for 20 years. Can anyone shed some light on what I need to do to get my AC working? It is not blowing cold, and I still have the stock R-12 system.

I have been told several ways to convert it from R-12 to 134A; 1 person said all I need are connector conversion kits to switch out the fittings, and then Evacuate the system and then recharge with 134A;

The other said that I have to swap out all parts(compressor, receiver/dryer, etc) with 134A parts.

Can someone tell me what process is correct?

Thanks!!
 

packer0440

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I believe that you need the new compressor as well as receiver dryer+fittings, other than that I think you should be good given that other parts are in good condition. Most likely the compressor leaks anyway after so long, and I think it has to be updated to accept R134. The new receiver dryer will also have the correct desiccants that work with R134; the stock one is not compatible. Also be sure to get a new orifice tube and replace as many o-rings as possible.
 

Nad_Yvalhosert

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I've been doing retrofits for about 20 years. I havent changed the oil in the last 15. Much as "common knowledge" says it's not compatible, I haven't seen one single compressor failure due to lack of internal lubrication.
Also, contrary to the previous post, ONLY change the o-rings that you interact with. If they're sealed and not leaking with R12, they're not gonna leak with R134a.

Due to age, absolutely change the oriface tube and the drier. Measure the amount of oil that you can drain out, and add the same plus 2 more of PAG oil. (The stuff that is compatible with both 12 and 134)

Lastly 80%. Charge with 80% of the R12 capacity. That's important, dont overcharge it.
My latest conversion is on an '85 Pontiac Parisienne. OE compressor and condenser are intact and are staying.

People may decide to contradict me, that's fine. I'm just giving you my double decade experience here in New Yuck. Granted we only get 3-4 months of heat, but A/C system does get used by the heater system to dehumidify and defrost the windshield.
 

Erik the Awful

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An R-12 system filled with R134a won't cool as well without a compressor upgrade. Being in Texas, you probably want the compressor upgrade. That's what I'm planning for my stepside when I finally get around to tearing into the heater/AC box again.
 
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