Verify with a digital voltmeter that the polarity is not reversed.
Disconnect the converter from the RV's positive battery terminal with an Allen wrench.
Connect a 120-volt shoreline power source to the RV.
Test the output voltage at the positive and negative terminals on the converter's front with a digital voltmeter set to direct current. Proper voltage tolerances vary by model and manufacturer, but generally the voltage should read between 13.3 and 13.9 V. If the readout is zero, check to see whether the reverse battery protection fuse or fuses are blown. If they are, replace them and retest the voltage.
Check the circuit breaker that supplies 120 volts of AC power to the converter. Reset the breaker if it is in the "tripped" position. If it trips again immediately after resetting it, replace the converter.
Set the voltmeter to measure AC power, and then use it to test the outlet into which the converter is normally plugged. If the outlet power reads between 103 and 130 V AC, but the converter's output is still zero, then replace the converter.
