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Ask GM Tech (Cam) Your Own Question
GM Tech (Cam)
GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 15201
Experience:  GM Grand Master Technician 2007. 14 years experience.
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We have a 2003 Chevy Express box truck... The heater does

Customer Question

We have a 2003 Chevy Express box truck... The heater does not blow any hot air. Its only cool air and only blows out the top defroster
Submitted: 1 year ago.
Category: Chevy
Expert:  Dave Nova replied 1 year ago.

Does the engine reach normal operating temperature? Is coolant filled to proper level?

Customer: replied 1 year ago.
to both questions
Expert:  Dave Nova replied 1 year ago.

The different modes are vacuum controlled. (floor, dash vent, defrost) Check vacuum hoses in engine compartment. See if there is vacuum going to plastic reservoir located under battery mount tray.

With engine running and at operating temperature, feel both heater hoses. Are they both hot? Is one or both cooler than radiator hose?