75psi on high and low side

[getterdun]

Vehicle: 2005 Acura RL
Problem: Gauge reads 75psi on both high and low side after adding 1 can of R134a
Prior action: Have replaced compressor twice and expansion valve once
* First compressor replacement was because original one was leaking. This was a cheap Chinese compressor.
* Second compressor was after installing first replacement the pressures were equal: same as above. This is an expensive Denso compressor.
* At this point, the only thing I knew to do was to replace the expansion valve. But, even after this, the pressures are the same.[/list]

At a loss for what to do next. Will appreciate any help. Thanks.

[Cusser]

It sounds like the AC clutch on the compressor is not engaging. Is the CENTER part of the compressor actually turning, or just the outer rim of the pulley?

[JohnHere]

I would approach this by first recovering the refrigerant that's in it now, pulling a good vacuum for at least 30 minutes, and weighing-in the factory-specified charge of 19.0 ounces of R134a. Then take LP and HP gauge readings at an engine speed of 1,800 RPM with the A/C system on and report the pressures here. Leak-checking the system at this point is also a good idea since you thought the system was low on refrigerant and you added a can (hopefully without any sealer or enhancers in it). The 75 PSI readings you have now sound to me like static pressures (A/C system and engine off).

[JohnHere]

If you have only about 12 ounces in it (one can), it is way too low. And as Cusser alluded to, the compressor won't engage.