Durango 2WD V8-5.7L VIN 2 (2007)
Blower Motor Relay: Description and Operation
Controls - Rear
Description
DESCRIPTION
The blower motor relay (1) for the rear heating-A/C system is a International Standards Organization (ISO)-type relay. Relays conforming to the ISO
specifications have common physical dimensions, current capacities, terminal function and patterns (2). The rear blower motor relay is a
electromechanical device that switches battery current from a fuse in the junction block directly to the rear blower motor. The rear blower motor relay is
energized when the relay coil is provided a voltage signal by the ignition switch.
The rear blower motor relay is located in the junction block (JB) in the passenger compartment.
Operation
OPERATION
The ISO-standard rear blower motor relay is an electromechanical switch that uses a low current input from the ignition switch to control the high current
output to the rear blower motor. The movable, common feed relay contact is held against the fixed, normally closed relay contact by spring pressure.
When the electromagnetic relay coil is energized, it draws the movable common feed relay contact away from the fixed, normally closed relay contact
and, holds it against the fixed, normally open relay contact. This action allows high current to flow to the rear blower motor.
When the relay coil is de-energized, spring pressure returns the movable relay contact back against the fixed, normally closed contact point. The resistor
or diode is connected in parallel with the relay coil, and helps to dissipate voltage spikes and electromagnetic interference that can be generated as the
electromagnetic field of the relay coil collapses.
The rear blower motor relay terminals are connected to the vehicle electrical system through a receptacle in the junction block (JB). The inputs and
outputs of the rear blower motor relay include:
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The common feed terminal (30) receives fused battery current at all times.
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The coil ground terminal (85) is connected to a ground at all times.
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The coil battery terminal (86) receives battery current from a fuse in the junction block (JB) through an ignition switch output (run) circuit only
when the ignition switch is in RUN.
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The normally open terminal (87) provides battery current output to the rear blower motor through the rear blower motor relay output circuit only
when the rear blower motor relay coil is energized.
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The normally closed terminal (87A) is not connected to any circuit in this application, but provides a battery current output only when the rear
blower motor relay coil is de-energized.
The rear blower motor relay cannot be adjusted or repaired and must be replaced if found inoperative or damaged. Refer to the appropriate wiring
information for diagnosis and testing of the ISO-standard relay and for complete HVAC wiring diagrams.
