Got in my truck this morning and turned on the air, set blower motor to first setting. Nothing, went all the way to highest setting and blower turned on. What causes this? Is the dash control bad or the motor. Like I said the blower only comes on at the highest setting.

 

If it only works on the highest setting its your resistor block. I can't tell you exactly where it is but if you can follow the wires from the blower motor back you'll find it.