My A/C started leaking refrigerant at the base of the pressure switch located at the drier/liquid accumulator. I noticed it when the A/C stopped cooling due to ice blockage on both the front and rear evaporators. There was oil around the base connection. Any advise on replacing this switch without pulling all the R134A from the system? I was thinking of releasing some of the R134A by depressing the schrader valve to lower the system pressure and just unscrew the leaky switch and install the new one. This way, no air will enter the system. Then just recharge the system using a recharge kit from the auto parts store. Any comments? Thanks.