Commander 4WD V8-4.7L VIN N (2006)
Compressor Clutch Relay: Description and Operation
RELAY-A/C CLUTCH
DESCRIPTION
The A/C clutch relay (1) is an International Standards Organization (ISO) micro-relay. Relays conforming to the ISO specifications have common
physical dimensions, current capacities, terminal functions and patterns (2). The ISO micro-relay terminal functions are the same as a conventional ISO
relay. However, the ISO micro-relay terminal pattern (or footprint) is different, the current capacity is lower, and the physical dimensions are smaller
than those of the conventional ISO relay.
The A/C clutch relay is located in the power distribution center (PDC) in the engine compartment.
OPERATION
The ISO-standard A/C clutch micro-relay is an electromechanical switch that uses a low current input controlled by the powertrain control module
(PCM) to control the high current output to the A/C clutch field coil. 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 A/C clutch field
coil.
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 A/C clutch relay terminals are connected to the vehicle electrical system through a receptacle in the power distribution center (PDC). The inputs and
outputs of the A/C clutch relay include:
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Terminal (30) receives fused battery current at all times.
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Terminal (85) receives a ground through the A/C clutch relay control circuit only when the PCM electronically pulls the circuit to ground.
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Terminal (86) receives fused battery current through an ignition switch output circuit on gasoline engine models or from the ASD relay on diesel
engine models, only when the ignition switch is in the Run or Start positions.
-
Terminal (87) provides battery current to the A/C clutch coil through the A/C clutch relay output circuit only when the A/C clutch relay coil is
energized.
-
Terminal (87A) is not connected to any circuit in this application, but provides a battery current output only when the A/C clutch relay coil is
de-energized.
The A/C clutch 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 micro-relay and for complete HVAC wiring diagrams.
