Simplest and easiest way to relay headlights

[hemihotrod402]

I have found that I have a lot of time on my hands recently, so I figured I might as well do little things for the car. First thing is going to be relaying the headlights. I have seen numerous ways to do it, but what is the quickest and simplest? Im kind of an idiot when it comes to the wiring of the car, and I have no idea where to start. I have been studying the diagrams that Dave posted when he did his, but still not figuring any of it out. What parts are needed to do it, and where can I find them?

[87gtVIC]

No understand my post!? Well first off try and learn more about the function of relays. Once you become familiar with them you can understand their function. Basically you normally have 5 posts on a relay (some relays have 4 but here I will deal with 5). Okay so you have post 85 and 86. One is for the triggered power (in this case the stock headlight low beam for one relay and the stock high beam signal for the second relay) and the other post if for a ground. Those two posts make up the coil within the relay. When the coil receives power from the stock headlight wire it will trigger the coil to direct a new power source to the headlights. The new power source is always on post 30. When the coil is triggered the constant power at post 30 is redirected to post 87 which leads to your headlights. Just look this over and draw it out yourself. Drawing it out allows you to really understand what is going on. Oh and just for kicks when no power is applied to the coil post 30 normally directs power to post 87a.

[91grandmarquis]

What exactly does the relay do? Does it just take a load off the switch? If so how?

Sorry but I suck at auto electrical, it is a wonder I managed to re wire 2 of my guitars as well as I did.

[87gtVIC]

The relay takes an existing signal and uses a new signal to power something. In this case the relay takes in the headlight switched power and uses direct battery power to then power the headlights. It takes a severe load off of the headlight switch.

[sly]

hmm... I may do this to my car. Those old sealed beam lights sure don't help see much.

[hemihotrod402]

okay, where can I find the relays at? again, my electrical know how is minimal lol.

edit: also, is there a definitive parts list somewhere that shows exactly what I would need?

[87gtVIC]

All you really need is two relays (autoparts stores have them) eight female spade connectors (in case the relays do not come with a harness) couple heat shrinkable butt connectors (to connect the wires from headlight switch output to relay, then relay output to headlights and a ring teminal to get power from starter solenoid or battery and various lengths and gauges of wire and a fuse holder. Tell you what...I finished up the gauge pod and I would send you the two relays and the relay holder and the inline fuse holder with fuse I used with my first relay install free of charge with the gauge pod.

[hemihotrod402]

Thanks Dave!!! I'll study that diagram some more. Hopefully I will get it figured out. My dad and I have the house to ourselves tonight (that means garage time for until whenever we get tired) and I'll ask his input on it too. Sometimes, I honestly do not know what I would do if it weren't for this forum (I would just be left with CVN lol )

[sly]

use the 30 Amp relays (most auto stores don't carry smaller ones, but some do) just to be on the safe side.

[1990LTD]

The relay takes an existing signal and uses a new signal to power something. In this case the relay takes in the headlight switched power and uses direct battery power to then power the headlights. It takes a severe load off of the headlight switch.

hey man - do the headlights from both sides share common wiring? i saw you mention that you need two relays to do the job so i am assuming they do but i just want to be sure. is it just two circuits, one for highs and one for lows?

[1990LTD]

yeah I guess they do the more I stare at it, the more sense it makes. I don't know where all of the wiring is and where the relays are supposed to go but I think tracing wires off of the back of the headlights will probably answer my questions, no?

[87gtVIC]

One relay for low beams and one for high (others have done two for each). There is one wire looped between the four headlights for the high beam and one wire looped between the low beams.

[GoodSamaritan]

For those who have trouble understanding relays, here's a simple description of what they do for the beginners out there.

A relay reduced to basics is just a switch. Unlike the doorbell button on your house, you don't turn it on by pushing it and holding it, you use electricity to do it for you. When you put power to the relay, it's going to stay on until you turn the power off, just like you standing there holding that doorbell button, until you take your finger away. (note this is a bad example because many doorbells only ring once, unlike the old time buzzers,or a car horn, but you get my meaning)

This electricity is separated from whatever you are turning on and off.

So what you are trying to do with the relay mod for the headlights, is use the original light wiring to turn on the relays instead of your headlights. This means that the original headlight wiring will no longer be carrying (and losing a good bit of)the load. You can then use heavier, and shorter wire (*the longer/shorter a wire is, the more you lose before it gets to the headlights) to power the headlights straight from the battery.

With less losses in the system your headlights will be brighter.

Clear as mud?




* You can compensate for a longer run with heavier wire, or you can shorten the run and get similar results. Btw you won't gain anything measurable by going with a truly huge cable to power your headlights. I'd go a bit bigger than stock, and be done with it. By reducing the length, and powering it straight from the source, it will be more than sufficient.

[BigT]

I will say it again...awesome site! The creators/administrators have done an outstanding job. They make it easy to find topics you’re looking for to fix problems you have.

I installed two relays for my headlights due to working midnights now…and what a difference it is driving into work! I also replaced some of the lights because I think they have never been replaced before. In fact the driver’s low beam was so old the chrome backing was all but removed. You could see right through it.

Before I did the relay install, I was going to make a thread looking for off-road high beams to help me see. However, now the lights are so bright the reflection off a warning sign was too bright and I had to dim them! Now I can see for miles now!

Next project is an ignition kill switch/alarm. I plan to hide an on-off-on switch to switch from the starter to the horn.

Thanks again for doing great work!

[Grand Marquis GT]

Awesome!

You'll have to let me know when you're up for another Bowling Alley lunch