12V LED Lights and Light Bars

Where the lamp goes decides its color and function

Lamp color and function are tied to position. At the rear, stop and tail lamps are red and reverse lamps are white, while side marker lamps are red at the back and amber toward the front. Clearance lamps mark the top corners of wide vehicles. Look for a DOT or SAE marking if the lamp will be used on a public road, because decorative lamps may not meet the rules.

Vehicle-specific replacements, listed by year and model, usually bolt into the original opening and plug into the existing connector. Universal lamps need you to supply the mounting, with a grommet, stud or surface mount, and the wiring. Light bars are rated by output and length, and a long bar can draw many amps at 12 V, so match the wire gauge and fuse to the stated current.

Bulb base, LED load and flasher timing

Check the bulb base before the brightness. A 1156 has a single contact and a 1157 has two, for stop and tail in one bulb, and they are not interchangeable. Colored bulbs, such as green or amber, use the same bases, so confirm the number in the title. LED replacements are polarity sensitive in some sockets, so follow the maker's notes if one does not light.

LED lamps draw far less current than incandescent bulbs, and a flasher built for the old load may flash too fast, known as hyperflash. Fix it with an LED-compatible flasher or load resistors. Rated voltage matters too: a lamp marked for 12 V should not be wired into a 24 V truck circuit unless it states a wider range.

Questions about 12V LED Lights and Light Bars

Why do my turn signals flash fast after fitting LEDs?

LEDs draw much less current, so the flasher unit senses a fault and speeds up, called hyperflash. An LED-compatible electronic flasher or load resistors fitted in parallel with each LED lamp restore the normal rate. Resistors get hot, so mount them on metal away from wiring.

What is the difference between 1156 and 1157 bulbs?

Both have a similar bayonet base. The 1156 is single-filament, for one function such as reverse or turn. The 1157 has two filaments, for tail and brake in one bulb, and its offset pins stop it fitting a 1156 socket.

Can I put 12 V lights on a 24 V truck?

Not unless the lamp states a 12 to 24 V range. A 12 V lamp on 24 V overheats and fails quickly, and a resistor to drop the voltage wastes power as heat. Choose lamps rated for your system voltage, and check the connector and wiring match.