Checking For A Shorted Circuit

LINCOLN-MERCURY: 1991 CAPRI


ISSUE: Diodes attached to the main wiring harness (14401) and the engine control wiring harness (12A522) may be damaged if external power sources, such as battery chargers, are connected incorrectly.

ACTION: Test the diodes for evidence of damage and, if needed, replace them as required. Refer to the following procedure for service details.


AVOIDING ELECTRICAL SYSTEM DAMAGE

Avoid damaging the electrical system by taking the following precautions when connecting any external power source.

^ Only connect the power source to the car through the battery cable terminals.

^ Connect the power source negative and positive cables to the correct battery cable terminals.

NOTE: THE BLACK CABLE IS BATTERY POSITIVE (+). THE BLACK/YELLOW CABLE IS BATTERY NEGATIVE

Figure 1:

DIODE - MAIN WIRING HARNESS - CHECKING FOR A SHORTED CIRCUIT

If the engine continues to run with the ignition key in the OFF position and with either of the car doors open, diode (C2000) has short circuited. It is feeding 12 volts to the ignition switch. It is located on the main wiring harness, Figure 1.

Other indications of a short circuited diode (C2000) are:

^ The ignition switch is in the RUN position with the instrument cluster gauges operating, warning lamps illuminated and either car door is open.
^ When the door is closed, or the door sill mounted switch is depressed, the battery and fuel gauges drop to zero and the warning lamps are not illuminated.

^ The gauges and warning lamps return to the original condition when the door is reopened.

Figure 2:

Additionally, for turbo engine cars, diode (C262 & C263) may also be damaged, Figure 2.