REMINDER: Our marker lights DO NOT come on when the light bar is turned on, only when markers on towing vehicle are turned on.
If your light bar uses a circuit board with the 8 position plug on it, unplug the circuit board and inspect the wires going into it and verify that none of the wires have come loose. If they have, contact Custer Products. Turn the plug over and with the switch turned on, check the voltage from the black wire and the red wire that is catty-corner from it. It should read whatever your battery’s voltage is.
If your light bar has a circuit board that is hardwired into it, using a voltmeter, turn on the switch and check the voltage of other terminal with the black wire and the center terminal. It should read whatever your battery’s voltage is.
Check that the transmitter is fully inserted into the socket on the towing vehicle.
If using a 4 pin round or 6 pin round transmitter, spread the pins on the truck socket so that they make solid contact with the transmitter.
If your light bar has a 7 pin round, 7 blade flat, 6 pin round or 4 pin round socket on it, plug the appropriate cable into the truck and the light bar to see if it operates as a corded bar. If it does not operate as a corded bar, check that your truck socket is functioning.
The light bar will not operate off of the batteries if the voltage gets down too much below 9 volts, but the light switch LED can light with as little as 4 volts. Make sure that the light bar is fully charged or plug your light bar into your charger and test the functions of the light bar.
Test the light bar with the towing vehicle running, a battery that is operating close to 10 volts will not have enough voltage to allow the transmitter to send a signal to the light bar.