A/c on driver’s side blows much warmer than on passenger side even though they are set at the same temp. Mechanic has added more refrigerant with dye twice and cannot see a leak in the system. This works for a few weeks and then the problem returns. Any thoughts on what it could be?

 

So when your mechanic added freon what were the gauge readings. Was it low or how low was it. Now that the problem came back go have him put the gauges back on and see if you lost any freon. If not then you'll need to have someone looking at the mixing valves/dampers in the system. Did he check for any AC codes Also you might want to put an AC temp gauge (get on at Autozone or other stores) and see what your vent temps are. Need more info.

 

ah I had exact same problem a few years ago, my problem was had leak on vapor coil(located under the dashboard right beside the firewall). when refrigerant is low it doesn't fill the coil all the way that's why it only cool half way. when you recharge the AC it fills the coil all the way but if you have leak it get lower and doesn't fill the coil as suppose to. dealer asked $4200 for repair but it only cost me $180 for parts and it is not a easy DIY for sure. I hope you have leak other than coil where it's easy repair and cheaper repair good luck.