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H4 Wiring Harness Questions

Discussion in 'Lighting' started by 84 yota dude, Nov 12, 2017 at 3:28 AM.

  1. 84 yota dude

    84 yota dude

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    Jul 7, 2014
    Hi all

    Man I love this forum. I was asking a question in the 95 and older truck section and had another question about a headlight mod, sure enough there is a lighting section!

    I have a 1987 4runner. Let me just say the factory light output is terrible. I have done a great deal of reading on this upgrade and am planning to make my own replay harness. Attached is a picture of the schematic I drew up (I tried to scan it but the scanner wasn't working, will post scanned version later). Daniel stern's lighting website was very helpful, as I basically just copied his diagram. However, after learning about negatively switched headlights on Toyotas, I tweaked his diagram.

    My question for the electronic pros out there, does this look correct?
    My second question is what gauge wire should I run out of the relays to the headlights? I'm planning to run 12 gauge from the battery and 14 gauge for the ground wires. However after looking at H4 connectors, most use 18 gauge wire. That just seems too small in my opinion. I think I would rather run 14 gauge all around except for the 12 gauge power supply wires to the relays.

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