Operation CHARM: Car repair manuals for everyone.

Heated Glass Element: Description and Operation

Heated Mirror:




HEATED MIRROR SYSTEM
Electrically heated outside rear view mirrors are an additional factory-installed option on models that are equipped with the factory-installed dual power mirror option. Vehicles with this option can be visually identified by the International Control and Display Symbol icon for rear window defogger, which appears on the lower inboard corner of each outside mirror glass; or, by the heated mirror switch that is located in the lower left corner of the heater and air conditioner control unit face plate. The heated mirror system helps the vehicle operator maintain outside rear view mirror visibility during inclement operating conditions by keeping both outside mirror glasses clear of ice, snow, or fog. The heated mirror system for this vehicle includes the following major components:
- The heated mirror switch, including the heated mirror system solid state electronic control logic and timer circuitry, the heated mirror relay and the heated mirror system indicator lamp. All of these components are integral to the heater and air conditioner control unit on the instrument panel.
- The two outside mirror heating grids, which are integral to the power outside mirror units.

Following are general descriptions of the major components in the heated mirror system. See the owner's manual in the vehicle glove box for more information on the features, use and operation of the heated mirror system.

The solid state electronic control logic and timer circuitry for the heated mirror system receives battery current from a fuse in the Junction Block (JB) only when the ignition switch is in the On or Start positions. After the heated mirror system is turned On, the electronic control logic and timer circuitry will automatically turn the system off after a programmed time interval of about fifteen minutes. After the initial time interval has expired, if the heated mirror switch is depressed and released a second time during the same ignition cycle, the electronic control logic and timer circuitry will automatically turn the heated mirror system off after a programmed time interval of about five minutes. The heated mirror system will be shut off automatically if the ignition switch is turned to the Off or Accessory positions. After the heated mirror system is turned On, it can also be turned off manually by depressing and releasing the heated mirror switch a second time.

When the heated mirror system is turned On, the heated mirror system control logic and timer circuitry energizes the heated mirror system indicator lamp and the heated mirror relay. When energized, the heated mirror relay supplies fused ignition switch output (run/start) current from a fuse in the JB to the outside mirror heating grids located behind the mirror glass of each of the outside rear view mirrors. When energized, each of the outside mirror heating grids produces enough heat to warm the glass of the outside rear view mirrors.

Heated Mirror Switch:




HEATED MIRROR SWITCH
The heated mirror switch, the heated mirror system indicator lamp, the heated mirror system solid state electronic control logic and timer circuitry and the heated mirror relay are all integral to the heater and air conditioner control unit, which is located between the instrument cluster and the radio near the center of the instrument cluster bezel on the instrument panel. The heated mirror switch and the heated mirror system indicator lamp are visible in the lower left corner of the heater and air conditioner control unit face plate. The solid state electronic control logic and timer circuitry and the heated mirror relay are not visible, but are also located within the housing of the heater and air conditioner control unit.

The heated mirror switch, the heated mirror system indicator lamp, the heated mirror system solid state electronic control logic and timer circuitry and the heated mirror relay cannot be repaired. If any of these components is damaged or faulty, the entire heater and air conditioner control unit must be replaced. Refer to Heater-A/C Control for the location of the proper heater and air conditioner control removal and installation procedures.

The momentary-type heated mirror switch provides a hard-wired battery current signal to the heated mirror system electronic control logic circuitry each time it is depressed. In response to the heated mirror switch input, the electronic control logic and timer circuitry energizes or de-energizes the amber heated mirror system indicator lamp next to the heated mirror switch to indicate that the heated mirror system is turned ON or OFF. The electronic control logic and timer circuitry also energizes or de-energizes the heated mirror relay, which controls the feed of electrical current to the outside mirror heating grids.

The heated mirror system electronic control logic and timer circuitry is programmed to turn the heated mirror system Off automatically after about 15 minutes of operation. If the heated mirror system is turned On a second time following an initial time-out event during the same ignition switch cycle, the heated mirror system electronic control logic and timer circuit is programmed to turn the system Off automatically after about five minutes. When the electronic control logic and timer circuit detects that a programmed time interval has elapsed, it will automatically de-energize the heated mirror system indicator lamp and the heated mirror relay. The heated mirror system will also be turned OFF if the heated mirror switch is depressed while the system is turned ON, or if the ignition switch is turned to the OFF or Accessory positions.

OUTSIDE MIRROR HEATING GRID
Vehicles equipped with the optional heated mirror system have an electrically operated heating grid located behind the mirror glass of each power operated outside rear view mirror. The outside mirror heating grid consists of two thin laminations of plastic that approximate the outer dimensions and shape of the mirror glass. A single length of resistor wire weaves in a back and forth pattern between, and is held in place by the two thin laminations of plastic. The two ends of the resistor wire terminate near the inboard edge of the grid, where they are soldered to the ground feed and battery current feed wires contained in the power mirror wire harness. The heating grid is then sandwiched between the back of the molded plastic mirror glass case and the mirror glass, where it remains in direct contact with the back of the mirror glass at all times.

The outside mirror heating grids cannot be repaired and, if faulty or damaged, the entire outside power mirror unit must be replaced. Refer to Power Mirror for the location of the proper power mirror unit removal and installation procedures.

One end of the outside mirror heating grid resistor wire is connected to a ground feed at all times through a body ground screw located inside the left rear corner of the truck cab. Battery current is directed to the other end of the outside mirror heating grid resistor wire by the energized heated mirror relay when the heated mirror switch is in the ON position. As electrical current passes through the heating grid, the resistance of the wire in the heating grid converts some of that electrical current into heat. The heat produced by the heating grid is then conducted through the back of the mirror glass to help keep the glass clear of ice, snow or fog.