Just replaced my compressor, replaced dryer and expansion valve.

Vacuum on system, vacuum held for 30 minutes.

22oz R134 refrigerant added.

A/C is not cooling, low side pressure is 40 with A/C off
When A/C is is turned on and compressor clutch engages pressure drops to zero

Could it be a leak? might be to small to notice

Any suggestions or guidance will be greatly appreciated.

already searched but couldn't find why the pressure drops to zero when clutch is engaged.

Thanks.

 

There's probably a restriction/obstruction in the system that is preventing proper coolant circulation. Did you flush the system and replace the receiver/dryer?

 

Yes, dryer and expansion valve were replaced.

Thanks for the reply.

 

Well... If the compressor is off... and you only have 40 psi... you are too low on a charge. You should absolutely not have a 0 reading with the compressor on either. That's assuming the compressor is actually working.

Is the compressor OEM New, OEM used, or replacment part New?
When you pulled a vacuum, how long did it take to pull?
What kind of gauges are you using?
Assuming gauges have a r134 reading on them...
When you charged the system, how long did it take to put 22oz in?
How do you know you put 22oz in?
What r134 measuring system did you use?
Do the high side lines get hot or stay cool?
Is the dryer cool or hot while running?

There is no way your car should be reading 40psi with compressor off and 0 with it on, if there is 22oz in the system.

Off the top of my head, your system should be reading 120-140 psi with the compressor off... rough estimate.

MAYBE 35-50 with the compressor on. You can't charge properly by pressure though. I deal with HVAC for a living, and if you can answer those above answers as accurately as possible... I can help narrow down your problem.