Blower Motor Relay: Testing and Inspection

WARNING: ON VEHICLES EQUIPPED WITH AIRBAGS, DISABLE THE AIRBAG SYSTEM BEFORE ATTEMPTING ANY STEERING WHEEL, STEERING COLUMN, OR INSTRUMENT PANEL COMPONENT DIAGNOSIS OR SERVICE. DISCONNECT AND ISOLATE THE BATTERY NEGATIVE (GROUND) CABLE, THEN WAIT TWO MINUTES FOR THE AIRBAG SYSTEM CAPACITOR TO DISCHARGE BEFORE PERFORMING FURTHER DIAGNOSIS OR SERVICE. THIS IS THE ONLY SURE WAY TO DISABLE THE AIRBAG SYSTEM. FAILURE TO TAKE THE PROPER PRECAUTIONS COULD RESULT IN ACCIDENTAL AIR- BAG DEPLOYMENT AND POSSIBLE PERSONAL INJURY.

Fig.16 Blower Motor Relay:

RELAY TEST
The blower motor relay is located in a wire harness connector that is secured to the heater- A/C housing behind the glove box on the passenger side of the vehicle, next to the heater-A/C wire harness connector in the passenger compartment. Remove the relay from its connector to perform the following tests:
1. A relay in the de-energized position should have continuity between terminals 87A and 30, and no continuity between terminals 87 and 30. If OK, go to Step 2. If not OK, replace the faulty relay.
2. Resistance between terminals 85 and 86 (electromagnet) should be 75 ± 5 ohms. If OK, go to Step 3. If not OK, replace the faulty relay.
3. Connect a battery to terminals 85 and 86. There should now be continuity between terminals 30 and 87, and no continuity between terminals 87A and 30. If OK, see the Relay Circuit Test procedure in this group. If not OK, replace the faulty relay.

RELAY CIRCUIT TEST
1. The relay common feed terminal cavity (30) is connected to the blower motor. This terminal supplies fused battery feed directly from a fuse in the Power Distribution Center (PDC) when the relay is energized, and ignition switched battery feed from a fuse in the fuse block module through the blower motor resistor when the relay is de-energized. There should be continuity between this cavity and the blower motor feed circuit cavity of the blower motor wire harness connector at all times. If OK, go to Step 2. If not OK, repair the open circuit as required.
2. The relay normally closed terminal cavity (87A) is connected to the blower motor resistor output. When the relay is de-energized, terminal 87A is connected to terminal 30 and provides the blower motor resistor output to the blower motor feed circuit. There should be continuity between this cavity and the blower resistor outputs circuit cavity of the blower motor resistor wire harness connector at all times. If OK, go to Step 3. If not OK, repair the open circuit as required.
3. The relay normally open terminal cavity (87) is connected to a fused battery feed from the PDC. When the relay is energized, terminal 87 is connected to terminal 30 and provides full battery current to the blower motor feed circuit. There should be battery voltage at this cavity at all times. If OK, go to Step 4. If not OK, repair the open circuit to the PDC as required.
4. The coil battery terminal cavity (86) is connected to the high speed output contacts of the blower motor switch. When the blower motor switch is placed in the high speed position, fused ignition switch output is directed to the relay electromagnetic coil to energize the relay. There should be continuity between the cavity for relay terminal 86 and the high blower motor relay control circuit cavity of the blower motor switch wire harness connector at all times. If OK, go to Step 5. If not OK, repair the open circuit as required.
5. The coil ground terminal cavity (85) is connected to ground. This terminal supplies the ground for the relay electromagnet coil. There should be continuity between the cavity for relay terminal 85 and a good ground at all times. If not OK, repair the open circuit as required.