2005 Trailblazer Blower motor is completely inoperative
I have a 2005 Chevy Trailblazer and the heating / AC blower motor does
not spin at all on any setting. I have checked the voltage at the connector
and it baffles me. In position 0 it's zero volts. Makes sense. Position 1, 2,
and 3 it's 13.4 VDC. This makes no sense to me. This is a DC motor, no
logic, just a DC motor. I thought the way the speed was adjusted was by
lowering toe voltage to slow the speed. In position 4 (highest speed setting)
the voltage varies rapidly around 20 to 400 millivolts. I took the blower
motor out of the truck and on the bench applied 12V from a battery
charger, it spins strong and healthy. I replaced the resistor even though the
old one seemed to be fine, but that also (not surprisingly) did not solve the
issue. When it died, it died all at once. Just didn't work at all one day.
What confuses me most, why does the fan not spin if there is 13.4VDC at
the blower motor connector? I used the connector from the old resistor as
a test fixture and it worked fine so not a corrosion problem on the motor
power pins. I'm at a loss as to why applying power on the bench works, but
voltage measured in the car as ok does not spin the motor.
There is a technical bulletin on this that says there is a bad ground under
the carpet in some models, but I measured the voltage across the
connector. If the ground were bad wouldn't that show up as low voltage?
Unless it's ok until I try to pull current through it.. Any ideas?
