Grand Caravan V6-3.3L VIN R (2005)
Blower Motor Relay: Description and Operation
Front
Front Blower Motor Relay
The blower motor relay for the front heating-A/C system is an International Standards Organization (ISO)-type relay. Relays conforming to the ISO
specifications have common physical dimensions, current capacities, terminal functions and patterns.
The front blower motor relay is located in the integrated power module (IPM) in the engine compartment.
The front 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 blower motor resistor (manual temperature control) or the 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 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 a battery current input from the battery through a B(+) circuit at all times.
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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.
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The coil battery terminal (86) receives a battery current input from the battery through a B(+) circuit at all times.
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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 fused front blower motor relay output circuit 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 repaired and, if faulty or damaged, it must be replaced. Refer to the appropriate wiring information for diagnosis and
testing of the ISO-standard relay and for complete HVAC wiring diagrams.
