Heater control valve


Asked by Mar 05, 2016 at 02:30 AM about the 1994 GMC Sierra 1500 C1500 SL Standard Cab LB

Question type: Maintenance & Repair

I have a 94 GMC Sierra 1500, I have replaced the
heater core 3x the thermostat 2x and she is still
not blowing out hot air, I need to know where the
heater control valve is located

1 Answer


They don't use one, it is controlled with blend doors, and depending on the system type they are either vacuum controlled or fully electric servos. The only other reasons could be, a massive air pocket in the heater lines and the core, or no coolant flow from the engine to the core. Do both of the heater hoses get hot when running? The feed hose will be slightly hotter than the return.

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