Adjusting stock POA for r134

[71CHEVYSHORTBED402]

Originally Posted by engineer_gregh

My comments (in italics) on Tony's earlier post are based on my own experience in rebuilding the A/C on my 71 money pit. It blows 42 degrees with R134a.

Just for (*&()^, from my education to-date, this identifies the system and what's required for 134a conversion. Corrections welcome:

Original Evaporator: Works for R12 & R134a

Original Expansion valve: Works for R12 & R134a

Original POA valve: Works for R12 & R134a, though must be calibrated for what you're using.

Original Muffler: Does not work for R134a. Not true, it can be used with an adapter. R12 and R134a use different fittings for servicing.

Original hoses: Word is the original hoses do not work for R134a. Un-confirmed. Not true, but if your hoses are terminated with clamps versus crimped you should change them. If they are original and 40+ years old I would change them.

Original compressor: Works for R12 & R134a

Original O-rings: Do not work for R134a. Not true

Original Dryer: Does not work for R134a. Not true, but a new one at Auto Zone is $12.99 so change it.

Original Condenser: Works for R134a, but not as well as serpentine replacements, which remove heat better. The original condensers are tubed. I believe you meant parallel flow not serpentine. 100% correct although if you add pusher fans to the tubed typed condenser it helps in dissipating the heat.
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Thank you. I'd heard the dryer wasn't compatible. I don't remember who told me that, but I recall they being a good source. Doesn't mean they're right. Might also mean yeah it works, but for some reason, not as well long term. I have an NOS dryer, which adds some interest.

Surprised to hear O-rings are compatible. Perhaps I mistook "replace them anyway" with "doesn't work". Then again, might be another case of longevity.

Personally, I'm hoping a guy restores behind the muffler. It's not cheap, but the comfort knowing it's first rate is a nice option. I'm using 134a. Honestly, I'm good with the windows & vents open. Something to be said for having A/C when you need it, never mind everything works.

Though my muffler looks like new, and the adapter sounds great, like you say, the hoses (crimped) are pushing five decades. So new muffler & hoses.

Rebuilt compressor. And decal - I guess.

Dryer appears to be up in the air.

My condenser is thrashed. I'll get what works & mounts best......hopefully.

[Bigdav160]

The old XH-5 desiccant in the drier is not compatible with R134a. The pore size is wrong and the R134a/pag will slowly disolve the desiccant.

XH-7 is the preferred desiccant for R134a and should work for R12 also. Many companies are using XH-9 desiccant universally but XH-7 is still used in better brands.