Little heat from Side vents
 

Having an issue with the side vents producing heat and some with the center vent. With the heat on full blast and set to center with the blend mixer on full hot I get decently warm air out of the center vents, but barely even warm air from the side vents. The defrost and feet seem to work alright, but not as hot as I would like. The one vent that does produce very hot heat is the rear vent. It is much warmer than any front vent.

The fan is working fine so I doubt it is the FSR.

Anyone have any ideas?

I wonder if the switch is stuck for the temp. It might be reading it is hotter then it actually is. I wanted to say heater core, but you said you get hot air out of some vents.

Check the water valve. I just replaced one on a customers car for a similar condition. if the water valve is jammed and not letting enough coolant to the heater core, you will have strange low-heat conditions.