How to connect the three wires of high and low beam lights?
3 Answers
There are a total of 3 wires for the high and low beam lights, which are: one ground wire, one low beam control wire, and one high beam control wire. Connect the black wire to the chassis, the white wire to the low beam, and the upper filament will light up; connect the blue wire to the high beam, and the lower filament will light up.
When I first installed the headlights myself, I found the three wires a bit confusing, but it turned out to be quite simple once I figured it out. Generally, the ground wire (black or brown) needs to be connected to the metal part of the car body, ensuring it's securely fastened; the high beam wire (usually white) connects to the high beam position; and the low beam wire (blue or another color) connects to the low beam. I always recommend using a multimeter to test first to avoid burning out the bulbs by incorrect wiring. Don't rush into it—disconnecting the battery's negative terminal is the first step for safety. Also, check the car manual, as color codes may vary by model, and some cars use relays for control. Miswiring could cause lights to flicker or short-circuit. After finishing, start the car and test the lights to ensure proper high/low beam switching. Remember to wrap the connections with insulating tape to protect against moisture and oxidation. Take your time with this DIY task—it can save you a lot on repair costs.
Understanding the connection of these three wires is actually not difficult. The ground wire must be securely connected to the vehicle frame; the high beam wire should be directly connected to the high beam output terminal controlled by the relay; and the low beam wire connects to the low beam terminal. I often remind everyone to clean the contact points before wiring, use pliers to tightly press the connectors to avoid gaps. After connection, test the lights. If only one light turns on, the wiring sequence might be wrong—use a multimeter to measure voltage and distinguish the positive and negative terminals. What beginners often overlook is wire aging—check for damaged insulation and replace the wiring harness if necessary. Pay attention to abnormal lighting while driving, such as dimness indicating poor contact, and address it early to avoid battery drain. Safety is paramount—wear gloves to prevent electric shock.
