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Blower fan stopped working all together on my 03 trailblazer. As of yesterday all speeds worked and it was fine. The resistor usually goes one speed at a time but this just quit working . Any ideas ???? All fuses check out ok.Thanks in advance pjm

first check the fuse.

if thats good try running 12 volts directly to the motor. unplug the connector and run a length of wire from a 12v source like the battery positive terminal to one of the terminals on the motor. run a wire from the other terminal to a good ground. if the motor runs its good. if it dont run it needs to be replaced.

if the motor works check for continuity on the resistor block. or try to 'jump' the block by disconnecting it and jumping from the power input to output with the key on and blower switch on. if the fan works now the block is bad.

next try the same thing on the blower switch, either check for continuity or jump across the switch with the ignition on. if the fan comes on with the switch jumped, the switch is bad.

if none of this works u could be looking at a problem in the ac control head or possibly a broken or loose wire in the blower circuit.