No heat can not defrost windows. Not the termistat.
Did this just start happening??
Do you have air blowing out the vents, blower motor working??
Are you letting the vehicle warm up 1st??
First steps, ask your shop to
- Make sure that there’s engine-heated water going through the heater core
- that the dashboard coolant temp gauge is showing normal for a warm engine, mid-range
- that they can hear the hvac blower motor spinning
- that the hvac blend doors are in the correct position
- search their service database for hvac related tsb, customer service bulletins, and recalls
Bad HVAC actuator. Common failure on GMs and others. There are 3 or 4 of them under the dash. Hopefully is is one of the easy ones and not the ones requiring much of the dash be removed.
There’s only 2 actuators on this vehicle - one that controls the air flow (air inlet actuator) and one that controls the temp (temp valve actuator). Tough to make a diagnosis based on “No heat can not [sic] defrost the windows. Not the termistat [sic].” Could be low coolant, a plugged heater core, or an actuator if the fan works. When someone says they have no heat, presumably, they mean the fan blows air, but there’s no heat. Assuming has got me in trouble a few times though so…
There may be a problem with the blend door actuator.
The blend door is what controls whether you get cold/ hot or a mix of air from the HVAC system.
Tester