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2015 GMC Terrain defrost runs hot or cold

Defrost mode is either extreme hot or cold, it will not produce warm or cool air, why?

This probably won’t work but you can give it a try. I think to calibrate this system you turn the heater temperature control to all the way hot and selector to defrost before you turn the key on. Then turn key on. Wait 30 seconds. Then with key on turn to cold and floor. Wait 30 seconds. Should then be calibrated. If I’m wrong on this, someone might correct me but no harm done.

Thank you for the response.