SW2 L4-1.9L DOHC VIN 7 (1997)
Heated Glass Element: Diagnostic Trouble Code Tests and Associated Procedures
Circuit Operation
REAR WINDOW DEFOGGER SYSTEM
The rear window defogger system consists of a tinted glass that has a number of horizontal ceramic enamel compound element lines and two
vertical bus bars baked onto the inside surface during the glass forming operation. The feed terminal is soldered to the bus bar on the driver side
(SC/SL) or passenger side (SW). The ground terminal is soldered to the passenger side (SC/SL) or driver side (SW). The system is used to melt
ice or snow from the exterior surface of the rear window or to clear up condensation from the interior surface of the rear window.
Under some conditions, heat from the glass may not be detected by touch. The length of time required to remove interior fog from the back glass
are functions of temperature, atmospheric pressure and number of passengers.
This system uses a pod (area above radio) mounted switch with an integral ON indicator lamp. The ON/OFF function of this system is manual.
The off function of the system is also controlled by a timer in the chime module or by cycling the ignition switch.
The system only operates with the ignition in the Run position.
The rear defog switch is a momentary switch and when pressed On, the switch provides a ground input to the chime module to start the timer and
keep this circuit grounded for the appropriate time. The chime module also provides a ground path for current through an LED ON indicator lamp
in the switch assembly. When the relay coil is energized, current flows through the rear defogger element to ground.
A variable power density grid pattern is used on the rear defogger grid. The power density in the center section is greater than the power density to
either side of the center section. This design results in uniform clearing of the entire grid area.
CIRCUIT TIMING DESCRIPTION
The chime module provides the timing function and ground for the RR defog relay and On indicator. When the rear defog switch is pressed for the
first time in an ignition cycle, the rear defog element and switch indicator will go On and stay On for
15 minutes unless the ignition is turned to
either the ACC, START or LOC position or the rear defog switch is pressed again. Subsequent activation's of the switch, prior to cycling the
ignition, when the rear defog is Off will result in the same operation, except the time the defogger is On is reduced to
7.5 minute.
Circuit Testing - Components
IGNITION SWITCH
Refer to
Powertrain Management for Electronic Ignition System Diagnosis procedure. See: Powertrain Management
Repair/replace as needed.
If this component is good go to the next item indicated on the chart.
RR DEFOG RELAY
The window, RR Defog, fog lamp and A/C relays are interchangeable with each other.
Substitute another relay to see if the problem is fixed.
Repair/replace as needed.
If this component is good go to the next item indicated on the chart.
CHIME MODULE
Refer to
Audible Warning Device. See: Instrument Panel, Gauges and Warning Indicators/Audible Warning Device
REAR DEFOG SWITCH (Part of POD Switches)
Check the defogger On indicator. It should light when the rear defogger switch is On. The indicator should not be lit with the rear defogger switch
Off.
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The RR Defog relay should click when the rear defog switch is turned ON and click again when the rear defogger system times out or is
turned off.
Check rear defog switch resistance.
Switch resistance: Open when rear defogger is Off. Less than one ohm when rear defog switch is pressed On.
If On indicator has failed the whole switch must be replaced. If the dimming bulb has failed, it can be replaced separately.
Circuit Testing - Fuses
IGN3 FUSE
Location: Instrument panel junction block
Type:
10A Minifuse
Feeds: Circuit 641 and RR DEFOG relay coil
