Installing Relays for Lights and Replacing Dimmer Switch

[cv70chall]

Does anyone have photos of the headlight relay setup? Where exactly can I intersect the two harness wires for the headlamps? I've heard near the RAD support, under the battery and near the starter relay area.

Help and thanks-

 

[Chryco Psycho]

what I have done is to mount the relays near the start relay , the headlight wiring goes right past it & you have access to to 12V terminal on the start relay but by extending the wires 18 " or so you can hide them in front of the rad wall under the fender . You can cut into the headlight wires anywhere along their path so anywhere between the firewall & left headlights, the ground for the relays can attach to the battery ground on the rad wall right in front of the battery , this is also where the headlights are grounded .
You want to cut the red & purple headlight wires & use the dash side from the switch to trigger the relay on either 85 or 86 terminal & ground the other side terminal . then run a fuseable link from the start relay to the 87 terminal & connect the headlight side of the factory wiring to the 30 terminal . You will need two relays , one for low & one for high beam .
The dimmer switch is bolted to the floor under the carpet near your left foot , they often corrode & jam up , but with the relays there will be no load on the switch anymore .

 

[Adam]

On my 71 Challenger I am running dual electric fans and an electric fuel pump, each with its own relay. I mounted the relays to a small bracket and mounted them behind, and a little lower than, the drivers headlight buckets. There is enough room there, close to the battery and wiring, they are mostly hidden, and it gets them out of the hot engine compartment.

 

[cv70chall]

re:

what I have done is to mount the relays near the start relay , the headlight wiring goes right past it & you have access to to 12V terminal on the start relay but by extending the wires 18 " or so you can hide them in front of the rad wall under the fender . You can cut into the headlight wires anywhere along their path so anywhere between the firewall & left headlights, the ground for the relays can attach to the battery ground on the rad wall right in front of the battery , this is also where the headlights are grounded .
You want to cut the red & purple headlight wires & use the dash side from the switch to trigger the relay on either 85 or 86 terminal & ground the other side terminal . then run a fuseable link from the start relay to the 87 terminal & connect the headlight side of the factory wiring to the 30 terminal . You will need two relays , one for low & one for high beam .
The dimmer switch is bolted to the floor under the carpet near your left foot , they often corrode & jam up , but with the relays there will be no load on the switch anymore .

You mean the "hi-beam" switch on the floor, right? The dimmer switch is actually in the dash cluster below the headlight switch.
So, the wires I'm looking for are PURPLE and RED, located just by the starter relay, right? Is 18g wire OK to use with this?
Do you have a layout/ drawing of this? I have never done relay wiring and want to make sure it's right.

Thanks!

 

[Chryco Psycho]

Yes the Hi / lo beam switch on the floor , even 29 ga will work for the ground from the relay but 16ga minimum for the 12v power to the relay using crimp connectors you should not have to extend the purple or red wires at the relays .
Sorry I do not have a diagram handy

 

[cv70chall]

The Hi-Beam switch I have is brand new, so I'm not concerned about it.
I was under the impression that the relays get wired to the main harness and that I should replace the dimmer switch- as they handle all the current for the lights and mine seems to be going bad- causing "flickering" of the dash and headlights when the brake pedal is depressed.

 

[Chryco Psycho]

By using relays the power going through the headlight switch & hi/ lo switch is milli amps & only closes the coil in the relay , power is then switched directly from the starter relay to the headlight relay & out to the headlights , this dramatically shortens the distance power has to travel to the lights & takes power from the alt feed so the lights will be significantly brighter .

 

[Aussie Challenger]

Fitted relays to my Challenger, voltage at the headlights went from 5v to 13.5v and of course I can now see at night. I upgraded the Headlights to halogen at the same time, now there is no load on the switch or more importantly the firewall connector which can melt as resistance increases with our older vehicles.
Just did a google for a headlight relay, will try and attach it, very simple to do.

 

[cv70chall]

That's a real nice diagram! Thank you! What gauge wire can I use for this? I was thinking 18g which is fairly standard, OK? also, what size fuses do I use in the two links at the terminal block?
Can you also provide a link, part number or tell me where you picked up those Halogen lamps?

Thanks a ton!!

 

[Aussie Challenger]

You should be able to pick up at any better spare parts supplier, as my name implies I live in Australia and as I had to change my headlights over due to the way ours "dip" on low beam I upgraded to Halogen.

 

[Chryco Psycho]

I would use at least 16ga for the high power circuit , the fusable link can be smaller , say 18 ga basically just protects against a short & it will blow even if the ga is larger

 

[cv70chall]

I ordered two relay pigtails and will use those. Are they sufficient gauge size?

 

[Chryco Psycho]

Yes , they typically come with adequate wire size for far heavier loads than 2 headlights run

 

[Adam]

On my 71 Challenger I am running dual electric fans and an electric fuel pump, each with its own relay. I mounted the relays to a small bracket and mounted them behind, and a little lower than, the drivers headlight buckets. There is enough room there, close to the battery and wiring, they are mostly hidden, and it gets them out of the hot engine compartment.

 

[Aussie Challenger]

I mounted my relays on the inner guard skirt behind the battery, they don't get very hot there, I have seen them mounted below the battery for that concealed look.

 

[JDcuda]

or youcan just go to octane lighting an get ceramic h4 headlight relay harness and be done with it.