Re: hph

Posted by HH56 On 2022/12/14 21:49:24

Just some thoughts on the AC refrigerant. It originally had Freon 12 and today that will be expensive and very controlled to recharge (if you can even get it in your area). If you use R134A be aware of some possible issues because R134 might work or it might not work as well as hoped in a car of that age.

An issue may be the old lines. 134 has a much smaller molecule than 12 and there have been many reports after a changeover of refrigerant quickly leaking out. It was found rubber hoses, fittings and even some compressor seals in cars much newer than the Packard could allow the molecules to escape. The rubber hoses may need to change to a modern barrier hose that has a lining which will contain the refrigerant. The old SAE flare fittings may need to be opened and a varnish type sealant used on the flare surfaces to sort of glue them together. The compressor seal is an unknown and if it leaks, doubt there is anything that can be done. Compressor oil is another issue between the two refrigerants and there is a good chance what is there will not be compatible with 134 so you may need to flush the complete system to clear the old oil from any spots it might have collected before adding the new oil.

On the operation side, R134 has different pressures at the same temperatures than Freon. In the factory system the compressor stays energized and is always moving refrigerant making the system pressure based. Temp control method Packard used is via hot gas bypass where a valve opens and closes to shunt refrigerant allowing it to go to or be short circuited away from the evaporator to maintain the desired temperature. With that in mind, the original evaporator and modulator valves are calibrated for Freon pressures. With the pressure changes using 134 the evaporator valve may pass excessive amounts or may starve refrigerant to the evaporator causing operation issues. If the modulator valve fails to open or close at the correct fixed temp to bypass refrigerant the evaporator can freeze if temp goes too low or system will not cool very well if it bypasses refrigerant too soon.

Valves can be adjusted up to a point but it takes someone with a working knowledge of the old pressure based temp control methods. Hopefully you have a good AC guy because I would bet the average modern mechanic will not have a clue and can do serious damage if he just goes in and starts messing with things. Ask me how I know this to be a fact.