Troubleshooting a 12-volt battery charger is relatively easy. But you’ll need a voltmeter to troubleshoot most chargers. Since the charger is responsible for charging your vehicle’s battery, you want to make sure that it is working, that there is no resistance in the lead wires, and that the voltage coming out of the charger is what it should be.
Set the dial on the voltmeter to “Ohms” and test the voltmeter. Touch the leads of the voltmeter together. The reading should be “0.00,” but a variance of .05 is acceptable. “0.00” represents the resistance in the wires. No resistance means that an electrical current can pass through the lead wires the way it should without any resistance and that there is good connectivity (there is no break in the line).