How to Connect the Three Pins of an H4 Bulb?
2 Answers
The wiring method for the three pins of an H4 bulb is as follows: 1. The three pins are color-coded as black, white, and blue; 2. The black wire needs to be connected to the ground wire, the white wire to the low beam wire, and the blue wire to the high beam wire; 3. If the ground wire is not connected, the bulb will not light up, so it is essential to follow the correct sequence when installing the bulb. Additional Information: 1. There are two types of H4 bulbs: the first is 12V 65/55 watts, and the second is 24V 75/70 watts. Ordinary small vehicles use the first type. When replacing a faulty bulb, it is crucial to use the same model as the original to ensure the proper functioning of the vehicle's lighting system and avoid safety hazards. 2. A faulty vehicle bulb can compromise driving safety, especially at night. It is important to regularly check the bulbs for damage when driving at night. If any damage is found, replace the bulb promptly. The replacement process is quick and can usually be completed in just a few minutes.
I've been in auto repair for years and have replaced H4 bulbs countless times. Among the three pins, the larger one in the middle is usually the ground pin, which must be directly connected to the metal part of the vehicle body, such as a screw hole. The other two pins are for low beam and high beam—check the markings on the bulb: 'H' is for high beam, and 'L' is for low beam. When wiring, always turn off the engine and disconnect the negative battery terminal to prevent short circuits. Use a multimeter to test the corresponding positions of the wires in the vehicle. A common mistake is mixing up the low and high beams, which can cause the lights to flicker erratically when switched or even burn out the bulb. I always advise car owners not to cut corners—buying a matching socket is more reliable. After replacing it yourself, test the lights by turning the switch to ensure they function properly for safe driving.
