Ac compressor swap issues

[DrCharles]

You might even be slightly undercharged (but that's better than overcharged). A rule of thumb I've used many times is: high side pressure (in psi) 2.2 to 2.5 times the ambient air temp in F, measured in front of the grill. So on a 75F day that would be 165 to 187 psi.

Franklin makes some good points about the low side pressure and adjusting the switch slightly for the difference between R12 and R134a.

Your system does have a high-side cutoff too, I hope? If not, it's easy to install since the high-side port is physically near the compressor clutch wiring, at least on mine. Just another safety precaution.

 

[Booyah45828]

Good to see you got this running. I commented some on you fb post over the weekend, I don't get on here much except throughout the week.

You charge by weight, pressures are just a guideline. At idle I'd like to see 30-40 on the low side, high side around 300. But that is so dependent on so many variables. As such, if the weight is correct and those are your pressures then so be it. You can tweak it somewhat higher or lower due to it being a retrofit, but the idea is still the same. Charge by weight, in your case, by can.

Correct way to charge by gauge with any refrigerant is by factoring in superheat/subcooling. That is nearly impossible to do in auto ac due to the variable rpm nature of the compressor being driven by the engine, along with air flow differences passing through the condenser/evaporator.

 

[franklin2]

My truck has a high pressure pop-off. It's a 1989. I found this out when I wired in a electric fan and forgot to interlock the A/C system in with it. It makes a rather loud bang and lots of smoke. Didn't seem to hurt anything though.

I fill my systems till when I hold my hand in front of the vent for about 30 seconds, the cold air starts hurting my hand. Very scientific method.