Could be a faulty fan motor and/or switch.
if this system uses dex-cool flush the system
yes or computer
Check for vacuum leak or bad vacuum motor Check selector control
Switch problem? Cables disconnected?
If you mean the fan works on high only it's the blower motor resistor.
The blower motor resistor is defective.
needs new blower resistor
Because the other one is damaged. Usually water damage.
Try replacing the temperature control switch for the rear control cluster. Hope that that's the fix. Less than $20.
The 2004 Chevrolet trailblazer air conditioning fan switch has three settings. The switch can malfunction, and only work in the high setting.
blower motor resistor is bad
you need a new blower motor resistor