Pressure equalizing slowly at shutdown means that the expansion valve is closing like it should in that case. If it were stuck open, the pressures would equalize rapidly.

I think 18 oz. Consult the service manual or look for a sticker under the hood. Use of a larger condenser will change these amounts only slightly. Oil should not be added routinely. When the refrigerant leaks out or is removed by a recovery machine, very little oil typically escapes with it, so the ...

Find big leaks statically-- that is with the engine off. Inject a small amount of 134a into the low side and listen for where it is coming out. An electronic leak detector is useful here. If you use one, inject only tiny amounts of refrigerant so it doesn't flood the whole underhood area and cause f...

Tube and fin condensers are not good. The parallel flow is much better, the result of years of engineering effort on the best way to condense R-134a. Since R-134a is harder to condense than R-12, car makers quit using tube and fins when R-12 was banned. You may have trouble with the vacuum pump gett...

Turning by hand, does it just spin real easy like nothing is moving inside? I think the shaft can snap inside then it spins but won't pump.

Zero on the high side suggests that one or both of the manifold hoses are not coupling to the car properly. Any pressure you put in the low side should blow through the check valves in the compressor and appear at the high side even if it is not running. Some couplers have a knob on the top that mus...

Make sure you have the flow direction through the receiver-drier correct.

If drier came apart you need to deal with the particles downstream in the TXV and evaporator.

Parts such as the compressor case that are on the low side are only designed for 150 psi or so. Having the case burst could cause you injury or death.

Variable displacement compressor is better. It will emulate the operation of a POA valve system and run without cycling. You can remove the valve and use the POA eliminator kit as a pipe fitting (do not hook up the switch), or when you make up hoses just bypass it entirely. If you find the pressure ...

How cold is the evaporator outlet line getting? You need an accurate reading with a thermocouple, not an IR gun. It could be that the refrigeration is working OK but the heater core is reheating the air. Bypass the heater core for a test is another option. The ambient temperature needs to be mention...