Mike's Workshop Manuals: Service manuals for every vehicle
Home >> GMC >> 1999 >> Forward Control 7.4 B >> Repair and Diagnosis >> Heating, Ventilation & A/C (HVAC) >> HVAC Control Systems >> HVAC System >> Description

HVAC System: Description

Temperature control and mode selector lever control various A/C-heating modes. Blower switch selects any of 4 blower speeds. In A/C mode, a pressure switch on low pressure side cycles the compressor clutch to maintain a constant discharge air temperature. The heater system blends heated outside air with cooler outside air to obtain desired temperature. Various sensors control compressor and cooling fan operation.