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Control Module Test

WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 1990 Mercury Sable, 1990 Mercury Grand Marquis, 1990 Lincoln Town Car, 1990 Lincoln Continental, and 1990 Ford Taurus. However, it is still accessible from the selected car via links, so may be relevant.
  1. See TESTING PRECAUTIONS  and PRELIMINARY CHECKS before beginning test.
  2. Connect voltmeter between terminal No. 6 of module connector and ground. See Figure . Turn ignition switch to RUN position. Battery voltage should be present.
  3. If there is no voltage, check fuse or wiring from ignition switch to control module. If battery voltage is present, go to step 4).
  4. Connect voltmeter between terminal No. 1 of control module and ground (ignition still in RUN position). Turn heated windshield switch to ON position.
  5. Battery voltage should be present. If there is no voltage, go to SWITCH TEST. If battery voltage is present, go to step 6).
  6. Ensure module connector is plugged in. Connect voltmeter between terminal No. 12 of module connector and ground. Turn ignition switch to RUN position. Turn heated windshield switch to ON position. Voltmeter should read one volt.
  7. If voltmeter reads 12 volts, replace control module. If voltmeter reads one volt, go to SWITCH TEST below. If voltmeter reads zero, go to step 8).
  8. Connect voltmeter between pin No. 12 of control module and ground. Turn ignition off. Battery voltage should be present.
  9. If voltage is greater than zero but less than 10, replace control module. If reading is zero volts, check wire from alternator from output relay coil to control module. If battery is voltage present, proceed to step 10).
  10. With voltmeter connected as in step 9), start engine. Run engine at 1000-1500 RPM with no electrical load except windshield.
  11. Turn heated windshield switch to ON position and read voltmeter after 10 seconds. Voltage at terminal No. 12 should drop from battery voltage to about one volt a few seconds after windshield heat is turned on.
  12. If voltage drops to one volt, system is okay. If voltage stays greater than 3 volts or less than 0.5 volt, replace control module.
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