This is more than likely caused by the actual fan switch. As I am English, I have no idea what a Chevrolet Trailblazer is, or what it looks like even, but there are things which are common to all or many vehicles.
if all speeds do not work id say is a fuse, but if you just dropped one or two speeds. replace the blower motor resister. sells for $60.00 at the dealer.
neither,blower resistor or blower module controls fan speeds.
Resistor on the heater blower motor has failed
The common cause is a failed blower resistor.
If it works but not on all speeds or is almost making the car stall at idle if you turn the a/c on at a light Than its probably the fan motor resistor pack its $25-$30 at autozone and real easy and fast to replace.
the fuse you have two fuse box one under hood and one under the dash.
If only the HIGH SPEED is giving trouble but not the other speeds, check the HIGH SPEED relay mounted on the firewall facing the engine on the passenger side, they burn out easily If all speeds are giving trouble could be the power source or the blower motor
u need a new blower motor
What would cause the engine not to restart when hot Chevy Trailblazer 2007?
Yes, the ignition on a trailblazer can cause head lights to work improperly.
the reason blower does not work on all speeds, is the fan blower motor resistor. The resistor is a 4-5 step series circuit, 1 resistor is added for each reduction in speed. If one burns out then so will all speeds below it. The "high" circuit usually has a separate fuse and bypasses the resistor altogether.
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