First, check the fuse and all connections in the circuit for looseness and corrosion, ensuring the battery is fully charged. With the transmission in Park and the parking brake securely set, turn the ignition switch to the On position without starting the vehicle. Switch the heater controls to FLOOR and the blower speed to HI, listening for the blower operation. Switch to LO and listen again, trying all speeds. The blower motor resistor assembly is located on the blower motor housing under the right side of the dash. This has three resistor elements to provide low and medium blower speeds, and a thermal limiter resistor to prevent heat damage. If the thermal limiter circuit has been opened due to excessive heat, it should only be replaced with an identical part. With the resistor removed, visually inspect the limiter for damage. Check the resistor block for continuity between terminals, with resistances as specified. If these values are not met, replace the blower resistor. Locate the electrical connector at the blower motor and backprobe the brown/orange wire terminal, there should be at least 10 volts if the switch is not Off and the ignition is On. If not, there is a circuit problem. If there is voltage but the blower does not operate, backprobe the orange/black wire and connect it to a known good chassis ground. If the blower now operates there is a problem in the ground circuit. If it still doesn't operate, replace the blower motor. If the blower operates, but not at all speeds and the blower resistor has been checked, disconnect the electrical connector from the back of the blower speed switch and test the terminals for continuity, replacing the switch if the continuity is not as described. Locate the blower motor relay in the relay box under the center dash panel. Connect an ohmmeter to terminal 85, there should be resistance greater than 5 ohms between that pin and all others. Energize the relay with jumper wires applied to terminals 30 and 85. Connect a voltmeter to chassis ground and probe pin 87A with the positive lead of the voltmeter. Voltage should be greater than 10 volts. Attach another jumper from pin 86 to chassis ground and use the voltmeter to check for 10 volts or better voltage at pin 87. If the relay fails any of these tests, replace the relay.
