What steps verify that the lighting and signaling circuits function in a car?

• A. Replace all bulbs without testing
• B. Check fuses and relays, verify continuity, use test lamps or meters, and observe operation of each light and signal control
• C. Rely on the owner's manual only
• D. Assume circuits work if battery is connected

Answer: (B)

Verifying lighting and signaling circuits means confirming both electrical integrity and actual operation. Start by checking protection devices and power paths: fuses and relays must be good and not blown or stuck, since they protect the circuit and can block function if faulty. Then verify continuity along the wiring so there is a complete path from power through switches to the load. Use test lamps or a meter to confirm that voltage appears where it should and that there are no opens or high resistance in the circuit. Finally, observe the real behavior by operating each light and signal control to ensure the load responds correctly—bulbs light, signals flash, and switches behave as expected. This approach catches open circuits, bad connections, faulty relays, burned bulbs, and misadjusted controls. Replacing bulbs without testing can miss upstream problems, and relying only on the owner's manual or just having the battery connected doesn’t prove the circuits actually function.