Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSCHEVROLET1994G 10 VAN V8-305 5.0LREPAIR AND DIAGNOSISHEATING AND AIR CONDITIONINGTESTING AND INSPECTIONCOMPONENT TESTS AND GENERAL DIAGNOSTICSCIRCUIT OPERATIONVACUUM SYSTEMAUXILIARY HEATER VACUUM SYSTEM
1994 Chevrolet G 10 Van V8-305 5.0L
Auxiliary Heater Vacuum System
1994 Chevrolet G 10 Van V8-305 5.0LSECTION Auxiliary Heater Vacuum System
The auxiliary heater control switch in the instrument panel has four positions: OFF, LO, MED and HI. In any switch position except OFF, the auxiliary heater control switch routes battery voltage to the auxiliary heater blower motor when the ignition switch is in RUN, as explained in "Auxiliary Heater".
In addition, the switch routes vacuum from the vacuum tank to the vacuum actuator that opens the auxiliary heater hot water valve. When open, the hot water valve admits heated coolant to the auxiliary heater inlet pipe and auxiliary heater core.
When the auxiliary heater control switch is turned OFF, electric voltage to the blower motor is cut off and the hot water valve vacuum actuator is vented to atmospheric air to close the valve. This stops the flow of coolant to prevent unwanted heat.
In addition, the switch routes vacuum from the vacuum tank to the vacuum actuator that opens the auxiliary heater hot water valve. When open, the hot water valve admits heated coolant to the auxiliary heater inlet pipe and auxiliary heater core.
When the auxiliary heater control switch is turned OFF, electric voltage to the blower motor is cut off and the hot water valve vacuum actuator is vented to atmospheric air to close the valve. This stops the flow of coolant to prevent unwanted heat.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.