Heater (lack of) controls

[Windy Miller]

Anyone ever experienced a failure of heater control on one side of the car? Vents on drivers side blow cool air on every temperature setting other than "H" (i.e. 17-30). Vents on passenger side work correctly and blow air at a temperature appropriate to the desired temperature setting.

Overall, the performance of the heater seems to be a lot lower than it used to be, even when both sides are on "H" (yes, the enginge coolant level is normal!)