In many older cars, the headlight power travels a long distance through the light switch and thin wiring harness. This causes significant voltage drop: if the battery voltage is 13.8 V and only 12.3 V reaches the bulb, light output drops dramatically.

In a relay upgrade, the car's original wiring is used only as a "trigger" to activate the relay. The actual power to the bulbs is supplied via a thick cable directly from the battery through the relay. Result: Voltage drop reduces from e.g., 1.4 volts to 0.15 volts. Benefit: Light output increases visibly without needing illegal high-power bulbs (100W).

Relays: 3 units of standard 4-pin changeover relays (30A/40A). 2 units for low beams (one relay per side for safety). 1 unit for high beams (shared usually sufficient). Relay sockets: Make installation neat and simplify relay replacement. Fuse holders and fuses: Mandatory for fire prevention (e.g., 15A–25A). Wire: At least 2.5 mm² (preferably 4 mm² for main power from battery). Connectors: Blade connectors (preferably locking sockets).

Relay pins are numbered according to standard: Pin 30: Direct power from battery (fuse in between as close to battery as possible!). Pin 87: Power output to bulb. Pin 85: Ground (to body or battery negative). Pin 86: Control power (taken from the car's original light connection).

Low beams are used continuously. If you use only one relay and it fails while driving, the car is completely dark. Two relays ensure that at least one side remains lit in a failure situation.

Yes, you can. Since the original wire now only operates the relay, it's not stressed. You can take the control signal from, for example, the left side's original connector and use it to control both new relays.

Heat: They can melt the reflector or lens of the light fixture. Load: They further stress the original wiring, making voltage drop worse and often resulting in worse performance than a relay-upgraded 55W bulb. Legality: They are not approved for road use.

Position relays and fuses in a protected location, for example, in a plastic equipment box near the battery. Use proper crimping pliers for making connections. Remember to protect new wires with sleeving or spiral wrap to prevent chafing.