Chevy Heater Not Working? Diagnostic Advice

Many Chevy owners will have to deal with heater issues at some point during the life of their vehicle. If your S-10 isn’t blowing out hot air when the heater is turned on, for example, or your TrailBlazer vents aren't blowing out hot air at all, you have a problem. This guide will help you fix your heater before the colder seasons creep back up on us.

How the Heater Works

A vehicle’s engine produces heat as it is running. This heat has to be directed away from the engine to prevent damage. Therefore, coolant continuously passes around the engine to absorb the heat, then takes it to the radiator to be discharged into the ambient air.

Before the coolant flows thru the radiator, however, it runs through your car’s heater core (which is basically another radiator). The heat from the core is moved into the car’s cabin by a fan. Often times, a malfunctioning heater and a malfunctioning engine cooling system are often linked.

Causes of a Malfunctioning Heater

Diagnosing the cause of heater issues may require checking several different things. Here’s where to look when your Chevy’s heater stops working as it should:

Coolant Level

Many times, a heater issue arises when coolant fluid levels drop. If the amount of coolant in the system is low, the amount of heat being pushed into the heater core is lessened. The result will be less heat to hit the interior of your vehicle. Fixing this issue is easy, just fill the coolant to proper levels. However, if your coolant is low, you need to figure out why. Low coolant could be caused by something simple like a leak, or it could be indicative of a major engine problem (like a blown head gasket).

A Fuse is Blown

Heater failure may also be associated with a blown fuse for the control valve. If the heater is blowing cold air (rather than warm or even slightly warm air), this is a symptom of a blown fuse. Check the fuse cover to locate the control valve fuse and replace it is it faulty.

Failure of the Control Valve

Your Chevy’s control valve is like a switch that activates the flows of heat into the heater core. If the control valve is faulty, it will have to be replaced for functionality to be restored.

Symptoms of a bad control valve include:

*Temperature that doesn’t change with knob/control adjustment

*The valve itself is leaking coolant



*Note, not all vehicles are equipped with a heater control valve, consult your owner’s manual or a repair manual before trying to hunt it down.

Failure of the Fan Motor

Another reason for a lack of heat entering the cabin is a faulty fan motor. The fan is responsible for driving the heat radiated by the core into the interior. If the fan doesn't make any noise, or no air comes thru the vents (or if the air coming thru isn't blowing very hard), the fan motor may need to be replaced.

Heater Core Blockage

A blocked heater core may lead to the heater malfunctioning. The blocking of the tubes where the heated coolant flows will prevent the engine heat from entering the core, and no heat will be delivered to the cabin of your car. A hose replacement is recommend if this is the case.

Regular maintenance and checking the coolant levels will prevent most of these issues. Make it a point to check the system before winter is here again so you can stay nice and toasty in your car when it’s frosty outside.