issue with heat not working

aharrdar44 · January 4, 2014

I have an issue with my heat not working once my truck gets warm...don't know why but it was working the last time I drove it but it only blows cold air..anyone know what could be wrong? Its a 02 z71

tanked_darren · January 4, 2014

Could be a few things, is it manual controls? Blend door problem probably.

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brucelimerick · January 4, 2014

Could also be the thermostat in the engine is stuck open.

1997SierraSLT · January 4, 2014

The blend door actuator linkage on mine tends to bind up every once in a while. It gets gummed up with dust, etc.

txab · January 4, 2014

Could also be a plugged core

aharrdar44 · January 5, 2014

So how do I know what it is

gmtech4 · January 5, 2014

So how do I know what it is

garage will tell you ,,,,,maybe scan the HVAC module even

txab · January 5, 2014

To check the heater core, you can grab both hoses as it warms up. The inlet will be warm/hot and the outlet should be the same if flow is good. You might try this:

A re-calibration may fix you up. Try disconnecting the battery for

a few minutes. Reconnect it. Or remove the HVAC/ECAS fuse for a minimum of 10 seconds.

Re-install the HVAC/ECAS fuse.

Then turn the key to the on position, but

don't start. Don't touch the HVAC controls. Let them do whatever that

want to do. Air flow may change outlet points during this time. Wait

about 1 minute. Turn key off. Sometimes opening and closing the door can

make a difference as the vehicle controls see this as "cycle"

completion. Next start the vehicle and drive it a short distance and see

how it performs..