Headlight relays

[Theiskell]

Ok I have decided it’s time to add the relays to my headlights on my ’69. I was going to follow the below diagram, but ran into a small problem. The diagram only shows one green wire going to the high beam relay. I have three green wires in the front of the harness…1 dark green (I think it goes to the horns) 2 light green wires…from the wiring diagram I have for my year it looks like they go to the headlights.
My question is; do I hook both light green wires into the “high beam relay” From the diagram I have it looks like one green feeds the left lights and the other feeds the right. Am I correct here or,am I losing my mind.:huh:


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[Twin_Turbo]

The green comes from a single wire and splits near the radiator shroud. You can use either to trigger the relay, because thats all it does in the new setup. Trigger the relay to switch 12V power to the lamps. Same for the low beam, you'll have 2 of those (L&R beam) on the front end of the car too.

 

[Theiskell]

The green comes from a single wire and splits near the radiator shroud. You can use either to trigger the relay, because thats all it does in the new setup. Trigger the relay to switch 12V power to the lamps. Same for the low beam, you'll have 2 of those (L&R beam) on the front end of the car too.

Thanks that makes sense. When you say the “new” setup are you talking about rewiring the front plugs? I was planning on just using the original wiring in the front. I am not putting in other headlights, just trying to stop all the current from running through the switch. Should I run new wire to the lights???

 

[bobs77vet]

when he says the new set up he means the addition of the new relay along with the power wire to the relay, all of the existing wires can just be moved over to this relay. unless the original wires are frayed, broken or corroded you can use them again. the real benefit is the "fresh supply power" going into the relay to make your lights bright.

 

[mrvette]

when he says the new set up he means the addition of the new relay along with the power wire to the relay, all of the existing wires can just be moved over to this relay. unless the original wires are frayed, broken or corroded you can use them again. the real benefit is the "fresh supply power" going into the relay to make your lights bright.

Agree, but I measured my late camaro bulb install, with engine running and found a total of 1/2 a volt drop at the bulb, as opposed to alt output so I didn't bother...but they are stock bulbs, so I didn't expect much drop.....I don't do enough night driving to bother with high powered bulbs....

 

[Theiskell]

when he says the new set up he means the addition of the new relay along with the power wire to the relay, all of the existing wires can just be moved over to this relay. unless the original wires are frayed, broken or corroded you can use them again. the real benefit is the "fresh supply power" going into the relay to make your lights bright.

Agree, but I measured my late camaro bulb install, with engine running and found a total of 1/2 a volt drop at the bulb, as opposed to alt output so I didn't bother...but they are stock bulbs, so I didn't expect much drop.....I don't do enough night driving to bother with high powered bulbs....

I would think that voltage would be the same or close, but you would have a current drop going through the factory switch. Am I way off base here?

 

[mrvette]

when he says the new set up he means the addition of the new relay along with the power wire to the relay, all of the existing wires can just be moved over to this relay. unless the original wires are frayed, broken or corroded you can use them again. the real benefit is the "fresh supply power" going into the relay to make your lights bright.

Agree, but I measured my late camaro bulb install, with engine running and found a total of 1/2 a volt drop at the bulb, as opposed to alt output so I didn't bother...but they are stock bulbs, so I didn't expect much drop.....I don't do enough night driving to bother with high powered bulbs....

I would think that voltage would be the same or close, but you would have a current drop going through the factory switch. Am I way off base here?

NO, when measured with a DVM at the bulbs, and VOLTAGE drop due to a bad connection anywhere in the circuit, will be apparent at the bulbs.....

what happens is extra resistance is added into the circuit by bad switches, connections, too thin a wire/etc....that allows voltage drop....and yes there is less current with MORE resistance across any given voltage.....so you loose on two fronts, less voltage, across what you want to do the given job.....and also less current into the device/headlights in this case.....

since POWER in watts is Volts times AMPS/current......you loose on the volts, and on the amps too....so power takes a hit on both ends.....

CURRENT through ANY circuit has to divide equally.....can not have any variation in current drain, no matter where you cut the wires and splice in the current/AMP meter.....

:shocking:

 

[Theiskell]

when he says the new set up he means the addition of the new relay along with the power wire to the relay, all of the existing wires can just be moved over to this relay. unless the original wires are frayed, broken or corroded you can use them again. the real benefit is the "fresh supply power" going into the relay to make your lights bright.

Agree, but I measured my late camaro bulb install, with engine running and found a total of 1/2 a volt drop at the bulb, as opposed to alt output so I didn't bother...but they are stock bulbs, so I didn't expect much drop.....I don't do enough night driving to bother with high powered bulbs....

I would think that voltage would be the same or close, but you would have a current drop going through the factory switch. Am I way off base here?

NO, when measured with a DVM at the bulbs, and VOLTAGE drop due to a bad connection anywhere in the circuit, will be apparent at the bulbs.....

what happens is extra resistance is added into the circuit by bad switches, connections, too thin a wire/etc....that allows voltage drop....and yes there is less current with MORE resistance across any given voltage.....so you loose on two fronts, less voltage, across what you want to do the given job.....and also less current into the device/headlights in this case.....

since POWER in watts is Volts times AMPS/current......you loose on the volts, and on the amps too....so power takes a hit on both ends.....

CURRENT through ANY circuit has to divide equally.....can not have any variation in current drain, no matter where you cut the wires and splice in the current/AMP meter.....

:shocking:

:crap:See this is why I ask questions….I learn something new every day. Thanks for the explanation it makes more sense now.

 

[Theiskell]

I thought I would do a follow up on this mod. I have the relays wired in and there is a visible difference. Since I had two light green wires coming from the bulkhead connector I thought it would be a good time to test side by side. I wired one of the high beams through the relay and the other I left going through the switch. Turned on the lights and found a visible difference. I don’t have a light meter other than my eyes but the lights going through the relay are noticeable brighter. For me its worth doing, to keep from running the power through the switch, but the brighter lights are a nice bonus. Thanks Bird for the “how to” write up you did!:hi: