My AC/ Heater fan would not turn off by pushing off button or pushing arrow down to lowest level or even turning off the car. What can I do? It is a 2003 GMC Envoy.
It sounds like the blower module is faulty and would need to be replaced.
There's a technical service bulletin describing the blower motor control module not working or keeping the blower on in extreme low temperatures. Is it cold where you are?
Also, the module is only used with automatic climate control. If you have a manual system, it could just be a stuck relay.