S15/T15 Sonoma P/U 2WD V6-262 4.3L VIN W CPI (1994)
Air Door Actuator / Motor: Description and Operation
Air Distributor Duct
SYSTEM DESCRIPTION
Control of airflow through the HVAC module is regulated by vacuum-actuated doors. Outside air is either cooled or heated and then discharged
according to control setting. In case of vacuum line harness leakage or hose collapse, it is not necessary to replace the entire vacuum harness assembly.
Replacement can be made by cutting the hose and inserting a plastic connector. If an entire hose must be replaced, cut the hose off at the connector and
then attach a new hose directly to the vacuum solenoid control assembly.
VACUUM SYSTEM
All air valves except the temperature valve are controlled by engine vacuum stored in the vacuum tank in the engine compartment. The vacuum is routed
by a vacuum switch in the control assembly to any of the spring-loaded two or three-position vacuum actuators. One vacuum actuator is linked to each
air valve.
The vacuum switch in the control assembly is controlled by the mode lever or control knob. For each mode lever or control knob position, the vacuum
switch will direct engine vacuum to specific hoses and vent to normal air pressure the remaining hoses. When a hose is vented to normal air pressure, the
vacuum actuator's internal spring will expand and hold the associated air valve in one position. When vacuum is routed to the hose, the force of the
vacuum overcomes the internal spring pressure and moves the air valve to the opposite extreme of its travel. In this way, the mode lever or control knob
positions the air valves for the selected operating mode.
DUCTS AND OUTLETS
A system of ducts and outlets directs air to the passenger compartment. In cases of poor air output, defroster, heater, air conditioning, and vent ducts
should be checked for obstructions such as leaves, dirt, or objects which may have fallen into the ducts from the passenger compartment.
