Testing For Short to Ground

Testing For A Short With Test Lamp Or Voltmeter:

WITH A TEST LAMP OR VOLTMETER
1. Remove the blown fuse and disconnect the load.
2. Connect a test lamp or voltmeter across the fuse terminals (be sure that the fuse is powered).
3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the test lamp or voltmeter.
4. When the test lamp glows, or the voltmeter registers, there is a short to ground in the wiring near that point.

Testing For Short With Self-Powered Test Lamp Or Ohmmeter:

WITH A SELF-POWERED TEST LAMP OR OHMMETER
1. Remove the blown fuse and disconnect the Battery and load.
2. Connect one lead of a self-powered test lamp or ohmmeter to the fuse terminal on the load side.
3. Connect the other lead to a known good ground.
4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test lamp or ohmmeter.
5. When the self-powered test lamp glows, or the ohmmeter registers, there is a short to ground in the wiring near that point.

Finding Short With Short Finder:

WITH A SHORT FINDER
1. Remove the blown fuse leaving the battery connected.
2. Connect the short finder across the fuse terminals.
3. Close all switches in series with the circuit you are troubleshooting.
4. Operate the short finder. The short finder will pulse current to the short. This creates a pulsing magnetic field surrounding the circuit wiring between the fuse block and the short.
5. Beginning at the fuse block, slowly move the short finder meter along the circuit wiring. The meter will show current pulses through sheet metal and body trim. As long as the meter is between the fuse block and the short, the needle will move with each current pulse. When you have moved the meter past the point of the short, the needle will stop moving. Examine the wiring in that area for the short to ground.

FUSES POWERING SEVERAL LOADS
1. Refer to the schematic for the fuse that has blown.
2. Open the first connector or switch leading from the fuse to each load.
3. Replace the fuse.
^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test lamp or meter as described.
^ If fuse does not blow, refer to next step.
^ Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals.

Current Test:

TESTING FOR CURRENT
To test for current the meter must be connected in series in the circuit. Current measurements always involve a component being removed or disconnected from the circuit. The circuit current flows through the meter, which displays the current in amps or milliamps. The meter should have a rating higher than the expected current.

NOTE: Never use a meter set on a current scale to measure voltage. Severe damage to the meter, the circuit, or both will result.

Two commonly used locations for taking current measurements are at a fuse and at the battery.

To measure current in a Windshield Wiper Motor, for instance, the meter should be connected across the fuse terminals, after removing the fuse. The meter can be inserted in any circuit where a single circuit can be temporarily opened to make the measurement.

A special use of current measurement is the case of a vehicle whose battery goes dead with no explanation. In this case, refer to the Current Drain Test in Battery (refer to Starting and Charging). Starting and Charging