Grand Caravan V6-3.8L VIN L (2007)
Blower Motor Relay: Description and Operation
Operation - Rear
OPERATION
The rear blower motor relay is an electromechanical switch that uses a low current input from the front control module (FCM) to control the high current
output to the rear blower motor resistor (manual temperature control) or rear blower motor power module (automatic temperature control). 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 integrated power module (IPM). The
inputs and outputs of the rear blower motor relay include:
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The common feed terminal (30) receives battery current through a B(+) circuit at all times.
-
The coil ground terminal (85) receives a ground input through the front/rear blower motor relay control circuit only when the FCM electronically
pulls the control circuit to ground.
-
The coil battery terminal (86) receives battery current through a B(+) circuit at all times.
-
The normally open terminal (87) provides a battery current output to the blower motor resistor (manual temperature control) or blower motor
power module (automatic temperature control) through a fuse in the IPM on the rear blower motor relay output circuit only when the rear blower
motor relay is energized.
-
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 is de-energized.
The rear blower motor relay cannot be 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.
