79 Trans am: How much Freon?

Jolo

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I added r134 adaptors. How much R134 is needed to fully recharge the system?
 
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melsg5

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3.25 lbs. R12 10 oz oil, you will have to find conversion.
 

Jolo

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Thanks. I did a similar r134 conversion on an 80 mercedes 450 with no issues but I have read that the gm compressor and dryer are not compatible with 134. I don’t see how that could be correct. Any thoughts?
 

melsg5

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You have to flush the system and some feel poa valve has to be changed
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Jolo

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I am awaiting a reply from Classic Auto Air to determine if my 79 has a POA/Expansion Valve Seems post 73 models did not use the POA.
 

Jolo

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Thanks Melsg5 for the link. Very helpful. So here it is from Original Air Group/Classic Auto Air should anyone else choose to attempt this: my 79 has an orifice tube that needs replacing. I am looking into a bypass that allows the compressor clutch to engage the compressor as needed, rather than to run constantly when the ac is on.

The one issue I am having is finding a 3/8 x 24 high side R134a adaptor with a schrader valve installed. The low side (blue cap, large hose) is 7/16 x 20 and I have it, but not the high side. Advance Auto Parts has an Autocraft kit with a 3/8 high side fitting as does Auto Zone. I will check them out. Some of these kits do not have the valves. We shall see.

FROM ORIGINAL AIR GROUP
You will need to replace the O-rings, Search | Original Air Group; you will need R12 to R134a adapters, GM Charge Port Adapter Set R12 to R134a - Straight; you will need to replace the orifice tube, 1974-1999* GM Replacement Orifice Tube - Evaporator Mounted - White; you will need to flush your AC system and replace your compressor oil with 11oz of Ester oil, and you will need to replace your accumulator.
 

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