Having an issue with my AC. Not very cold. Compressor clutch is ok. Fans ok with varying engine temp. Haven't done the on board diag yet.
Measuring the pressure on the low side port it reads approx 30 psi with engine running and AC off. When the AC is turned on the pressure drops to zero. Does this sound like it needs filling up.

Thanks

 

It shouldn't even run if the pressure reads zero. Are you sure your gauge is accurate? Normal operating pressure should be in the 35-40psi range. I suggest you don't service it using that gauge until you have verified it's accuracy. An overfill and blown seals could result.

 

Check the attached document for pressures and also troubleshooting tips:-