6-10
HVAC - Manual
Recirculation is only available if the defrost mode is not
active. When the defrost mode is active, the
recirculation actuator positions the recirculation door so
that outside air is circulated to the windshield to reduce
fogging.
Electric Auxiliary Heater (C32)
Some models are equipped with an auxiliary electric
heater to assist in warming the passenger compartment
when the engine coolant has not sufficiently warmed to
operating temperature. The heater is a 12 V positive
temperature coefficient heating element located in the
HVAC case just downstream of the traditional heater
core. The HVAC control module will activate it when the
outside temperature is less than approximately 8°C
(46°F), the engine coolant temperature is less than
approximately 75°C (167°F), and the temperature blend
door is commanded to the full hot position.
Engine Coolant and A/C System
Refrigerant
For information on engine coolant, coolant flow, A/C
refrigerant, and the A/C refrigerant cycle, refer to
Heating and Air Conditioning System Description and
Operation.
2021 - Silverado 4500HD, 5500HD, and 6500HD Electrical Body Builder Manual
