Air conditioning

Probably worked well with R12. Has condenser and expansion valve been changed to one designed for R134a?

 

when i drove cabovers, the a/c system had to constantly fight the heat in the cab rising from the engine, and that was way back in the late 1970's for me.

there is only so much insulation under that cab, and if that truck is THAT old, i can bank that there are some pieces missing or loose, or wore out from the constant heat, allowing the heat into the cab.

there are R-134 kits that are used for automotive switch overs from R-12, and no major parts had to be replaced.

the only other thing i can think of, is that the radiator if it was ever replaced, is smaller that the original, and not allowing proper cooling of the coolant system, or maybe a few core rods are plugged up, rendering the radiator inefficient.

 

R12 was obsolete around the time I was born lol. I seem to recall that R134a is less thermally efficient then R12, so a bigger condensor and evaporator were needed when switching refrigerant.

 

The evaporator was always turning into an ice cube on mine, which made it worthless when the humidity was high.

 

Hoses on R12 systems are not barrier type hose. 134A is molecular smaller and can leak from R12 system hoses if your just installing the adapter fittings at service ports on older systems. I agree with @AModelCat 134A is less efficient. I remember getting some R12 systems well below 40* duct temp. Your never gonna get that with 134A much less on a retrofitted system.

 

You can still buy R12 if 609 certified.

 

Have you bought any as of late? I remember in the late 90's it was like gold and most wouldnt spring for the price, hence the retrofit market. Best bet was to stock up in the off season and adjust the price up in the summer. I remember @ $30 plus a pound you wanted to make for darn sure you fixed the leaks.

 

134 runs at a higher pressure, seems like a hundred pounds more, it is recommended to change hoses and all orings because of this, the old expansion valve will work, but it will work better with a new one.I have had my 97 since it was almost new and it has the artic insulation package, and the air is sure nothing special in it compared to my KW, I know the artic insulation is nothing like it is in my KW.

 

Last I checked closer to $70 per lb, but some vehicles don't have room for larger condenser or some nostalgia vehicles like to keep it original. Best bet for OP would be to check with something like this Builder Series - Vintage Air.