To troubleshoot a blower motor, first, check all circuit connections for looseness or corrosion and ensure a fully charged battery. Inspect fuse 2 in the fuse panel below the driver's side of the dashboard and examine the blower relay in the underhood fuse/relay box. If the relay fails the tests, replace it. With the vehicle in Park and the parking brake set, turn the ignition to ON without starting the engine. Locate the blower motor under the glove compartment, set heater controls to FLOOR and blower speed to 4, then listen for operation. Switch the blower speed to 1 and test all speeds. If non-operational, locate the electrical connector at the blower motor and back probe the Blue/red wire terminal. A voltage less than 10 indicates a potential circuit problem. If voltage is present but the blower is non-operational, back probe the Black/white wire and connect it to a good chassis ground. If it operates, check the circuit from the blower to the blower speed switch to the resistor to ground for a bad ground connection. If the blower operates but not at all speeds, inspect and test the blower resistor on the blower housing. If the resistance values are not correct, replace the resistor. If the blower operates but not at all speeds and the resistor is functional, remove the
A/C Switch, disconnect the electrical connector from the blower speed switch, continuity test, and replace the switch if necessary.