Home >> Porsche >> 2003 >> 911 Carrera 4S, Standard >> Repair and Diagnosis >> Heating, Ventilation & A/C (HVAC) >> HVAC Control Systems >> Heater, Diagnosis - 911 CARRERA (996) >> Fault code 28 - as of MY 2002 >> Footwell/defrost valve motor - No reaction to activation, signal unclear >> Possible cause of fault