RAM 1500 Truck 4WD V8-5.7L VIN D (2005)
Heated Mirror Relay: Description and Operation
The heated mirror relay (1) is a International Standards Organization (ISO)-type relay. Relays conforming to the ISO specifications have common
physical dimensions, current capacities, terminal functions and patterns (2). The heated mirror relay is a electromechanical device that switches battery
current through a fuse in the integrated power module (IPM) to the outside rear view mirror heating grids. The heated mirror relay is energized when the
relay coil is provided a ground path by the control circuitry within the A/C-heater control.
The heated mirror relay is located in the IPM in the engine compartment.
The ISO-standard heated mirror relay is an electromechanical switch that uses a low current input controlled by the A/C-heater control to control the
high current output to the outside rear view mirror heating grids. 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 outside rear view
mirror heating grids.
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 heated mirror relay terminals are connected to the vehicle electrical system through a receptacle in the integrated power module (IPM). The inputs
and outputs of the heated mirror relay include:
-
Terminal (30) receives fused battery current at all times.
-
Terminal (86) receives a ground through the defogger relay control circuit only when the A/C-heater control electronically pulls the circuit to
ground.
-
Terminal (85) receives fused battery current through an ignition switch output circuit only when the ignition switch is in the Run position.
-
Terminal (87) provides battery current to the heated outside rear view mirror grids through the heated mirror relay output circuit only when the
heated mirror relay coil is energized.
-
Terminal (87A) is not connected to any circuit in this application, but provides a battery current output only when the heated mirror relay coil is
de-energized.
The heated mirror 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 heated mirror system wiring diagrams.
