Dakota 4WD V8-4.7L Flex Fuel (2008)
Blower Motor Relay: Description and Operation
Operation
OPERATION
The blower motor relay is an electromechanical switch that uses a low current input from the battery to control the high current output to the 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 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 blower motor relay terminals are connected to the vehicle electrical system through a receptacle in the integrated power module (IPM). The inputs
and outputs of the 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) receives a ground circuit through the front control module (FCM).
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The coil battery terminal (86) receives fused battery current at all times.
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The normally open terminal (87) provides battery current output to the blower motor only when the 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 blower
motor relay coil is de-energized.
The blower motor relay cannot be adjusted or repaired and must be replaced if inoperative or damaged. Refer to the appropriate wiring information for
diagnosis and testing of the ISO relay and for complete HVAC wiring diagrams.
