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Headlight wiring using 1 relay

Discussion in 'GM Electrical Tech' started by Crawdaddy, Oct 6, 2011.

  1. Crawdaddy

    Crawdaddy Moderator Staff Member Platinum Contributor 1000 Posts

    I have a nifty wiring quandry I'm trying to solve for my friend's Dodge pickup. The short story is that large chunks of his factory wiring harness are crispified. Part of the wiring that's toast is the headlight circuit. So, he asked me to wire up a new setup. In the rain one day since he HAD to have the truck running, I wired up a circuit using what I had which was a SPDT switch, of insufficient rating. He used it like that for a long time before the switch wore out. Now he wants me to do it again, but this time, I have time and am going to do it right using relays.

    Trick is, I can't think of a wiring setup that doesn't involve 2 relays. Putting in 2 relays wouldn't be the end of the world, but it just seems so logical in my mind that I can do it with 1 relay. The only 1-relay circuit I've been able to come up with involves once again pulling the power for both lights through the switch which is not acceptable.

    So, anyone have a solution?
  2. Crawdaddy

    Crawdaddy Moderator Staff Member Platinum Contributor 1000 Posts

    Wow, noone even wants to comment on this? This must be a very interesting puzzle. I can whip up a 2-relay circuit that will allow the low beams to stay on with the high beams, so that might be the way I take.
  3. sstoner911

    sstoner911 New Member 1000 Posts

    So your wanting to wire the headlights and parking lights with one relay vs a separate relay for each?
  4. Crawdaddy

    Crawdaddy Moderator Staff Member Platinum Contributor 1000 Posts

    No, the goal was to wire up both high and low beams using one relay to power and switch between them. Switching between them is no problem, as it's a simple 87/87a setup, but figuring out how to also turn them off and power them directly off the battery with that same relay is what I can't figure out. I dont' think it's possible, but I thought I'd throw the challenge out.

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