Headlight wire sizes

[chewychevy67]

I am rebuilding my gmc 4 bulb wiring harness from the firewall to the battery. I'm charnging to led headlights and my harness looks OK but looking at the headlight wires they seem really tiny. I'm also adding relays to my headlights so I'll be making a custom harness for the head. Shod I be upgrading the wire size on this side of the harness on the other side of the relays to the lights or will the stock wire size be just fine?

[Dead Parrot]

Stock headlight bulbs draw somewhere around 6~8 amps max. Doesn't take a big wire to carry that current. Look at the size of the wire from the dim/bright switch. That is carrying the current for all four bulbs. No reason for the individual bulb wires to be larger then that one.

Probably worth while to make sure the socket contacts are clean.

[chewychevy67]

OK thanks

[bhap]

The wires running from switch to relays will be fine, they probably carry less than 1 amp. For the wires from relays to headlights, attached is a wire size chart for 12v that shows wire size by length of wire for various amp loads. 14 gauge is probably big enough, but 12 ga wouldn’t hurt - I don’t know how many amp LED lights draw. The wires from your power distribution block / battery to the relays need to be big enough to carry the load on each relay for the length of the run. Madelectrical.com is a good resource for information.

[chewychevy67]

These are the specs for the bulbs I'm using. My truck is a gmc so it has 4 headlights. Looks like 1.1 amps if that is correct (seems super low for a headlight?) per bulb and up to 24 watts per bulb on Brights.

[bhap]

That is low for headlight, but I guess that is a benefit of LED lights. Amps = watts / volts, so if the draw is 24w, it would be 2 amps. Maybe just clean up the connections and put some fresh harness tape on?

[kwmech]

Factory 16g wire is more than enough if you're converting to LEDs