Electrical - Voltage Drop Diagnostics
Group: ELECTRICALNumber: 08-BE-004
Date: JUNE, 2008
Model: ALL
Subject:
DIAGNOSIS VOLTAGE DROP
DESCRIPTION:
Excessive resistance in high amperage circuits may result in one or more of the following symptoms:
^ Blower motor speed slow down and the radio cycles off and on.
^ Intermittent headlight dimming during deceleration.
This bulletin provides the procedure to diagnose and repair the vehicle wiring grounds.
SERVICE PROCEDURE:
1. Start vehicle and turn on headlights (including high beam), air conditioning, and set the blower to maximum speed.
2. Using a known good digital volt-ohm meter (DVOM), perform a voltage drop test on the positive battery cable, paying particular attention to the leads to the Engine Room Junction Box (refer to photo). If the voltage drop is more than 0.2 volts on any of the leads, replace the Positive Battery Cable.
3. Perform voltage drop test on the negative battery cable. If the voltage drop is more than 0.2 volts, repair or replace the negative battery cable.
4. Perform voltage drop check to all body ground locations in the engine compartment. Check with the positive volt meter lead on the negative battery terminal and the negative lead to the ground locations. If the voltage drop is more than 0.2 volts, repair or replace the body ground terminal and/or wiring assembly.
5. Perform voltage drop check to all Engine and Transmission ground straps. Check with the voltmeter positive lead on one end of the strap and the negative lead to the opposite end. If the voltage drop is more than 0.2 volts, repair or replace the ground terminal and/or ground strap.
NOTE:
When repairing grounds, chase the bolt threads with appropriate tool, clean the harness terminal and apply a star washer between the bolt and the terminal eyelet. Do not sand or grind paint from the body.
WARRANTY INFORMATION:
Normal warranty operation code and times apply.