Original Headlamp Wiring

[Doppleganger]

Did these squares originally not use a relay for the headlights? I am starting totally from scratch so nothing to go on or to tie into the original setup for relays. In the ball of mess I removed wiring wise I found nothing that resembles a relay. I honestly cant remember ever driving the truck at night or if the lights even worked (very little did).

In the event they did have a relay, what did it look like or where was it located?

THX

 

[MarineOne]

No relay. All power goes direct through headlight switch. Lmc sells a heavy duty wiring harness that adds in a relay to take stress off that switch in cab

 

[Doppleganger]

I didn't think they used relays on anything but then see many old stock relays advertised as applicable, as if they did.

Thanks.

 

[75gmck25]

They have a horn relay, A/C blower fan relay and a dual battery charging relay, but I don't think there was one for the headlights.

 

[SirRobyn0]

That's why the headlight switch on old vehicles is so much bigger than modern vehicles, because all the power is running though the switch. Also why there are aftermarket relay kits available, the purpose is to remove the high load from the switch and also to reduce the voltage drop, which in turn equals brighter headlights.

 

[Randy and Easton]

@Doppleganger we are going to use the American Autowire version. Hope to install in a week or so

Headlight Enhancement Relay Kit

Headlight Enhancement Relay Kit

www.americanautowire.com

 

[Originalthor]

I'm really tempted to use one of these relays on mine when I do it. My outside light rarely gets left on so give myself 30 seconds or so of headlight time to get to the door.

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[Doppleganger]

I already have a relay box for under the hood so guess I'll wire them straight from that. Will have to eventually locate the trigger wires - most older cars I drove had a dual stepper relay for the headlamps - made grafting in HD wiring much easier. Amazing how crude and lacking the electrical system is in these. Makes me glad I gutted it. Some of the older cars I messed with had electrical diagrams that were 3 to 7 pages total (newer ones were 400pgs+). These weren't that much further ahead. lol

 

[Doppleganger]

I'm really tempted to use one of these relays on mine when I do it. My outside light rarely gets left on so give myself 30 seconds or so of headlight time to get to the door.

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Those are pretty cool. Used to wire them into fans on turbos to run 3 min after shut down to help with the heat soak.

 

[SirRobyn0]

I'm really tempted to use one of these relays on mine when I do it. My outside light rarely gets left on so give myself 30 seconds or so of headlight time to get to the door.

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That is a cool idea. I've got an LMC relay kit hanging around but have never installed it. Grabbing one of these relays might be motivation to do so. My wife's minivan and even my 96 Grand Cherokee has headlight timers which can sure be handy in the Jeep when I have to park it by the barn in the dark in the winter time....

 

[Girth]

I already have a relay box for under the hood so guess I'll wire them straight from that. Will have to eventually locate the trigger wires - most older cars I drove had a dual stepper relay for the headlamps - made grafting in HD wiring much easier. Amazing how crude and lacking the electrical system is in these. Makes me glad I gutted it. Some of the older cars I messed with had electrical diagrams that were 3 to 7 pages total (newer ones were 400pgs+). These weren't that much further ahead. lol

I need to look into this for myself.... since the previous owner stabbed in some relays, but I'm VERY skeptical of their wiring.

When I built a relay harness for my CJ5, the "trigger" was the original headlight harness itself. One of the existing headlight plugs got connected to my new harness, and that fed the relays. When you pull on the switch, that 12v signal would go to the relays, and from the relays was a whole new harness, with plugs for the headlights, but the load was now provided direct from the batt. So basically.... you know where your trigger wires are, if you build it like that. One important consideration was ensuring good grounds too.

 

[Doppleganger]

I need to look into this for myself.... since the previous owner stabbed in some relays, but I'm VERY skeptical of their wiring.

When I built a relay harness for my CJ5, the "trigger" was the original headlight harness itself. One of the existing headlight plugs got connected to my new harness, and that fed the relays. When you pull on the switch, that 12v signal would go to the relays, and from the relays was a whole new harness, with plugs for the headlights, but the load was now provided direct from the batt. So basically.... you know where your trigger wires are, if you build it like that. One important consideration was ensuring good grounds too.

More I look at the wires with the Painless kit, the more I think the circuits that require a relay - these will be my trigger wires. Lighter stuff like tail and turn lights, interior lights, horn, etc - wire it like it was. PO so butchered mine that none of the original wires were salvageable.

 

[Girth]

More I look at the wires with the Painless kit, the more I think the circuits that require a relay - these will be my trigger wires. Lighter stuff like tail and turn lights, interior lights, horn, etc - wire it like it was. PO so butchered mine that none of the original wires were salvageable.

That stuff wouldn't need or really benefit from a relay anyways. The idea of the relay is so high draw stuff can pull the Amps it needs, (direct from the battery, via the relay) without a voltage drop across long circuit, multiple connections, and other things that generally increase resistance.

In my opinion, it'd probably be easier keeping it mostly as originally designed, and only modifying it where needed. That way you run into less "Why doesn't this work?" issues, and won't end up having to figure it out from scratch. You're gonna need most of the original circuits (or their replacement) to trigger the relays, that's a given. You're not eliminating any wiring, you're actually adding additional wiring, to make use of the relays.