Dual Zone A/C - pass side not as cold driver side

[TMS]

I thought I would pass this discovery along.

I've had 2018 MY car about 6 months and now the heat is here. I have really been using the A/C as of late and recently noticed that when the dual climate control is set to Sync, the passenger vents warmer air than the driver side. In fact, I have to turn the passenger side down about 7 degrees cooler than the driver for a temperature match.

I researched every thread I could find with solutions ranging from heater valve, to stuck blend door, to bad temperature sensors, to low refrigerant. None of these seemed to fit my situation as the passenger air was not necessarily warm, just not chilly when synced. And by dropping the temp on the passenger side I could get the air nice and chilly like the driver side.

After a couple of weeks like this and driving solo during this time, I thought I would reach over and feel the air temp coming out of the passenger side vent by the door and compare it to the pass. side console vent. Well, I found that the far vent (next to the door) was completely closed. So I opened the vent and bam, the passenger side began cooling and matching the driver side temp when in Sync mode (Note to self, last time wife was in the car, she shut the vent off complaining it was too cold).

Then I began testing this. I closed the passenger door vent again. Back to same problem. Opened back up and then shut the driver door vent and now the driver side console vent began blowing air warmer when in Sync than the passenger console vent.

So there you have it. If you experience the same kind of issue, check for closed vents first.

I don't why it would do that. I have my theories but nothing certain. If anyone knows why the system behaves like that, this inquiring mind would like to know.

Stay cool!