I'm not getting any heat in my '02 A4. The two hoses are both hot (although one is definitely hotter than the other) so I will probably flush the heater core, but I don't expect it to fix the problem. I pulled the codes and I'm getting the following:

00604 Back Pressure Flap Motor Position Sensor
00735 Recirculation Flap Motor Position Sensor
01592 Sensor For Air Quality
01842 Potentiometer actuator For Temperature Flap Right

The 01842 code could be associated with heat, but I'm not getting any out of either side. Anyone have any ideas?