Resistor coils that rob power to slow the motor are burned up. A new one at the dealer is about $80.00.
Why are you replacing the switch? If the fan works only on high speed, replace the fan resistor. There was a TSB for this.
either the switch or the fan motor
Replace the blower motor resistor.
faulty switch, replace it(the one on your climate control panel)
Bad ignition switch.... took me forever and lots of money to find. Replace it and the fan will be fixed.
Possibly resistor pack on blower motor needs replacing
(1) Faulty fan switch -OR- (2) the resistor on the circulating fan has gone bad.
If you are saying the blower motor only works on the high speed setting, then the problem is a bad HVAC Resistor Pack.
u need a new control button switch the button that has 3 nobs on it that control temp .i had same problem only works on 5 right.
The 2004 Chevrolet trailblazer air conditioning fan switch has three settings. The switch can malfunction, and only work in the high setting.
there is a resistor on the fan motor that has gone bad, some models have a resistor unit mounted near the fan in case this happens.
replace the blower fan resistor located under the dash behind the glove box