head light relay mod

Hey guys I am wanting to relay the head lights in my 71 Demon pretty much right now..

I need to know which wires are FOR SURE the head light wires -

I found these in my 68 Dodge Dart/Charger/Coronet factory service manual - found a 71 diagram online and colors are the same

Black - ground
Violet - low beam
Red - high beam

I have a diagram of how the relay's are powered up, and pinned so I'm covered there, just need a confirmation of which wires to tap into.

Tap into the ones that make your lights come on.

Seriously, the wires that go to your bulbs right now are the wires you want to use to activate your relays.
Then you run a new larger wire to power the headlights with the relays.

On my own car I used a relay for each filament on each bulb and used the existing headlight power supply wires to activate the relays for each.
This way if I loose a relay I don't loose both bulbs, but just one. (the filament that relay controls)

I have Bosch 5 pin 30/40 amp relays 1 for each low and high beam circuit.. only using 4 pins currently - and power will not be wired to them as I forgot to get a inline fuse earlier today..

I had to repin my pigtails to have the correct color wires, on the correct terminal on the relay but I plan to tap into the factory wiring to make it all work, I could run a new wire to each light but that's a lot of work in my opinion

I did this same thing to my old 1983 Mustang GT and that had worse condition wiring than my Demon so I'm more than confident the factory wiring will handle the load - plus I hardly ever drive at night (can't drive the car right now currently)

Just wanting to finish up the wiring in my car is all.. this headlight relay, electric fans, and mod/ wire the under dash stuff is all that's left (cut the amp gauge wires, wire volt gauge, wire wideband o2 gauge)

Funny how a Dodge from 71 that has sat for 10 years currently - has better condition wiring than a 12 year newer Ford LOL

I already redid the engine harness, deleted the VR, swapped a Toyota 120amp alt, and rewired the stock electronic ignition

The wires come directly from the headlight dimmer switch on the floor and then go out to the lights. You should be able to figure out which two of the three go out to the lights themselves.

Use one relay for the high and one for the low beams. My relays are on the radiator support. Before I re-wired the entire car, I was able to just interrupt the factory wires there and splice in the relays.

zac_F71 said:

Hey guys I am wanting to relay the head lights in my 71 Demon pretty much right now..

I need to know which wires are FOR SURE the head light wires -

I found these in my 68 Dodge Dart/Charger/Coronet factory service manual - found a 71 diagram online and colors are the same

Black - ground
Violet - low beam
Red - high beam

I have a diagram of how the relay's are powered up, and pinned so I'm covered there, just need a confirmation of which wires to tap into.

Click to expand...

The red and the violet come right out of the bulkhead connector in the lighting harness on the way to "across" the rad support. So depending on where you are mounting the relays, you cut those harness wires in a convenient spot.

Be careful how you fuse them. I would at the very least, fuse each relay separate, that way if you develop a problem in high, you still have low, and vise versa. Don't use too small a fuse to prevent "nuisance" blows and keep the fuses away from engine heat

67Dart273 said:

The red and the violet come right out of the bulkhead connector in the lighting harness on the way to "across" the rad support. So depending on where you are mounting the relays, you cut those harness wires in a convenient spot.

Be careful how you fuse them. I would at the very least, fuse each relay separate, that way if you develop a problem in high, you still have low, and vise versa. Don't use too small a fuse to prevent "nuisance" blows and keep the fuses away from engine heat

Click to expand...

FWIW: I've been using one 20A fuse for my relayed headlights (both powered on the same fuse) that is zip tied onto the harness between the battery and the inner fender for about 7 years and I've never had it blow once. Even if it did blow out (and I didn't have any fuses in the car), I could just get out my jumper wire and jump the relay to basically "make it stock" and I could get home no sweat.

I plan to get 1 25amp fuse for relay power- pretty confident I got it wired and I carry spares in the car for the electric fans, alternator, and the lights, so not to worried about being SOL with no lights in an emergency lol

HUGE thanks guys! I will report back later tonight if they work I need to figure out how to mount my fan controller, then wire that, then move to inside the car for the little bit of wiring needed to install the 2 gauges, and a glove box light. Then pull the light harness out and rewrap it for final install..

You should get a light tester for your electrical drawer in your tool box to sit along side an electrical multimeter if you have one.

With these it has a sharp point on it, a light in its body, and a long wire w an alligator clip. You clip the alligator clip wire end to any good body ground then with the headlamp switch on, you probe the wires in the LH inner fender about where the battery is. Using the tip of the light tester you pierce the insulation on the wires to find the one that lights up the tester. The point needs to touch the wire. If its on low beam the low beam feed wire should make the light tester light up. Once thats found, switch it to high beam and probe the other wires in the bundle until you find the high beam wire that lights the tester up.

Another solution is to download the proper schematic off the net, or get a nice full color version for your car fully laminated off ebay like i did for about $10 well worth having IMHO.

Matt.

I have a test light just no power in the car, that's why I asked repeatedly for confirmation of which wires..

I'm doing this wiring to be able to power up the car.. I coulda left the lights for later, but wanted to rewrap the harness before installing it

Hopefully tomorrow the under dash wiring will be done, and I can get the positive battery cable swapped out then I can power it up and see if it starts on fire or not.. It shouldn't I've triple checked every wire I have cut or replaced and the worst that will happen with the lights is they won't work, I'll just repin the pigtails so they work if that happens