98 buick regal AC one side cool

I have a 98 regal LS, it has a due zone control. Now only the passenger side blow cool air (and not at the full strength ), even I turned both temprature control knobs to coolest. I started to have this problem earlier this year (April), and had a mechanic recharged the R134. It works for a while and then both side could only blow warm/hot air after a couple of months. I recharged the R134 by myself, but only the passenger side blow cool air. I checked the pressure and seems the refregin is in the high-side of the normal range already. Any hint about what might be problem?

Maybe the passenger side blend door actuator. I'm thinking it's an electric motor.. Anyone care to refresh my memory?

Welcome to AF.

First thing you need to do is get the leak resolved. The system should be leak tested. There is a high probability you have a leaking seal at the compressor or somewheres in the system. A low or improper refrigerant charge may cause uneven cooling across the evaporator even with the Dual Comfort Temp Climate Control. If the reading at the low side port is abnormal or high then proper diagnostics should be run comparing high side with low side readings with proper gauges.

I had a similar problem with my '99 Regal LS where the driver's side was not cool but the passenger side was. The charge was low so I had the system evacuated and re-charged with 2 lbs of R134a. It worked fiine for a few months but started the same problem again. I had a slow leak at the compressor and had to replace it.