I have a 2008 Honda CR-V with 160k miles. I live in temperate S. Cal so dont need the heater all that much but recently noticed that the left and left center vents give cold air, but the right center (dont know about far right, cant reach that far) gives warm. I dont recall it being that way in the past.
If I turn off the AC the left vents go to a more neutral temp but I only get warm out of the center right (and possibly far right).
I'm hoping this isnt one of those situations Scotty mentioned where taking apart the dash to fix the heater gets real expensive.
Probably blender door.
I mean those are quite easy to test, just see if the AC does the same in cooling mode - by having better conditioned air on one side.
I remember going in deep and diagnosing blend doors on my Ford - it just ended up just needing an AC refill, but I guess this probably has little to do with her/s case as heating probably uses a heater core instead.