Dodge Durango

 Service Manual

Heating and Air Conditioning » Diagnosis and testing
Blower motor relay

RELAY TEST

The blower motor relay (Voltage Reduction Relay or VRR) (Fig. 6) is mounted with a single screw directly to the instrument panel's structural plastic inside the glove box opening, next to the left-side energy-absorbing bracket (Fig. 7). Remove the blower motor relay 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 6 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 Relay Circuit Test in the Diagnosis and Testing section of this group. If not OK, replace the faulty relay.

Fig. 6 Blower Motor Relay

Fig. 7 Blower Motor Relay (VRR) Location

1 - BLOWER MOTOR RESISTOR CONNECTOR

2 - BLOWER MOTOR RELAY

3 - BLOWER MOTOR CONNECTOR

4 - GLOVE BOX LAMP CONNECTOR

RELAY CIRCUIT TEST

For circuit descriptions and diagrams, refer to Air Conditioning/Heater in Wiring Diagrams.

(1) The relay common feed terminal cavity (30) is connected to fused battery feed directly from a fuse in the Power Distribution Center (PDC), and should be hot at all times. Check for battery voltage at the PDC cavity for relay terminal 30. If OK, go to Step 2.

If not OK, repair the open circuit to the PDC fuse as required.

(2) The relay normally closed terminal cavity (87A) is not used for this application. Go to Step 3.

(3) The relay normally open terminal cavity (87) is connected to the blower motor. 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 continuity between the PDC cavity for terminal 87 and the blower motor relay output circuit cavity of the blower motor wire harness connector at all times. If OK, go to Step 4. If not OK, repair the open circuit to the blower motor as required.

(4) The coil battery terminal cavity (86) is connected to the ignition switch. When the ignition switch is placed in the On position, fused ignition switch output is directed from a fuse in the junction block to the relay electromagnetic coil to energize the relay. There should be battery voltage at the PDC cavity for relay terminal 86 with the ignition switch in the On position. If OK, go to Step 5. If not OK, repair the open circuit to the junction block fuse as required.

(5) The coil ground terminal cavity (85) is connected to ground. This terminal supplies the ground for the relay electromagnetic coil. There should be continuity between the PDC cavity for relay terminal 85 and a good ground at all times. If not OK, repair the open circuit as required.

ADDITIONAL RELAY CIRCUIT TESTING

• The relay common feed terminal cavity 30 is connected to the low side of the blower motor. When the blower switch is Off and the ignition is On, there should be battery voltage present on this circuit.

  When the ignition switch is On, the voltage at that point should vary based on blower switch position.

• The normally closed contact cavity 87A is connected to the resistor block cavity 3. Check this circuit by turning the blower switch to High and cycling between Heat and A/C modes. The voltage in the Heat mode should be approximately 2 volts. The blower switch must be in High blower speed position during this check.
• The normally open contact on cavity 87 is tied to both the resistor block cavity 6 and the HVAC blower switch cavity 6. Check for continuity on this circuit.
• The coil B+ contact cavity 86 is connected to an ignition run start feed. Battery voltage should be present on this circuit when the ignition switch is in the Run position.
• The coil ground (-) cavity 85 is connected to the HVAC switch cavity 2 as well as the JTEC and A/C high pressure switch. Battery voltage should be present on this circuit when the ignition switch is in the Run position and a Heat mode is selected on the control head. When an A/C mode is selected, the voltage at this point should be less than 1 volt.
• If the blower motor does not operate, or only operates in some modes, check for a faulty connection at the VRR, or defective blower motor relay (VRR).

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Blower motor relay

Blower motor resistor

Blower motor switch

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Low pressure cut-off switch

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