System Testing
- Turn ignition on. Ensure defogger is off. Connect an ammeter in-line with battery. Turn defogger on. If marked increase in amperage draw is not noted on ammeter, go to step 4). If marked increase in amperage draw is noted, go to next step.NOTE: Indicator light illumination does not confirm system operation. It only indicates that power is available at relay output.
- Verify system operation by feeling glass. After 3-4 minutes of operation, a distinct difference in temperature between grid lines and adjacent clear glass should be felt. If operation is as specified, go to next step. If operation is not as specified, go to step 4).
- Using a voltmeter, touch negative lead to terminal "B" and positive lead to terminal "A". See Fig 1 . If voltmeter indicates 10-14 volts, system is functioning properly. If voltmeter needle deflects severely, check for short circuit.
- Confirm ignition is on. Ensure heated glass feed wire is connected to terminal or pigtail and ground wire is properly grounded. Ensure fusible link and control circuit fuse are okay. Ensure all electrical connections are secure.
- If system is still inoperative, check for defective control switch or timer relay. Check if all grid lines are broken or if one of the feed wires is not connected.
- If system operates but indicator bulb does not light, service A/C, heater or ATC panel. For wiring details, see WIRING DIAGRAMS .