Started having problems this past summer with the AC. Would set both passenger and driver temps to lowest setting and would cool the van fairly quickly and then every once in a while the driver side vents would blow out hot air for about five to ten seconds while the passenger side would still be blowing cold air. Now in the fall as the outside temps require heat, I'm having similar problems. Set both sides to high and that seems to work until it starts getting too hot so I drop down 1 step from high which is 85 on the display and it used to get just a tiny bit cooler, now it seems to drop ten to fifteen degrees. Not very cold outside air but just a big jump where I'm going to have to go back to high again. Any ideas where to look first? Seems like it would be a faulty thermostat. Thanks.

 

You may want to have the HVAC system checked for codes. You could have a blend door not operating correctly.

 

Thanks for the suggestion.