HVAC issues

So it seems like I am heading for the dreaded blend door or some other HVAC issue. Had to use the heat for the first time in a while and I am getting lukewarm air in driverside and passenger side is nice and hot. Used the AC later in the same day (about the only thing I still like about SoCal is the weather) and cold in the passenger side and lukewarm on the driver. I can fiddle with the controls and eventually get it to work the same on both sides but fear i am just buying time at this point.

While I only have 86k on the clock I am at 14 years old with the truck. I guess I got good years out of it.