A continuity check is necessary to determine if there is a break in the circuit.
1. Remove voltage from the circuit and check the circuit for continuity with a light bulb with a power source connected.
2. Connect the light bulb wires to the ends of the circuit (or to the positive end and vehicle ground); if the control lamp lights up, there are no breaks in the circuit.
3. If the light does not light up, then there is an open somewhere in the circuit.
4. In the same way, you can check the switch by connecting a test light to the switch terminals.
5. After turning on the switch, the control lamp should light up.