Headlights and Relays

[oldblue1968chevy]

I got my relays from advanced auto for a $1.25 (a dollar and 20 something), thats apiece.

Bought the 10guage wire for about $10 and I already have the rest of the stuff

[ERASER5]

My biggest reason to install relays was to lower the current coursing through my wiring harness. All headlamp current only goes from the battery to the lights now. Since I have a GMC, my high beams are significantly brighter now.

[hatred]

Originally Posted by Roadmarks

@hatred, The idea is to get more volts and amps to the headlights. I did it by using a couple of new external switches and new heavier wire hooked more or less directly the battery. To make my life easier I used switches that could be thrown electrically called relays and used the original headlight switch and dimmer combo to do it! That's really all there is to it.

Yah I can visually see and understand the need for it to be done, but when I read how you guys did it or see pics of it my mind shuts down and I start drooling lol. Just don't understand HOW to do it.

[Stocker]

Maybe this diagram will help



And a couple threads from the FAQ section of the electrical forum:

http://67-72chevytrucks.com/vboard/s...d.php?t=182351
http://67-72chevytrucks.com/vboard/s...d.php?t=188478

[mrein3]

Another important thing in my opinion to think about when doing headlight relays is the headlight switch you'll be saving.

Back in my shop days I replaced alot of headlight switches. All that lost voltage has to go somewhere. Where it goes is it is turned into heat which eventually destroys your headlight switch.

I use 10 gauge wire for everything between the battery and the lights. For the circuit to turn on the relay I use the stock wiring. All you're doing is converting your existing headlight switch into a relay controller.

Back in about 1985 when I installed halogen sealed beams in my '71 Monte I thought man! Look at all that light. When you get your relays installed and use those same halogens you'll wonder why people waste their money on Hellas and other aftermarket lights.

And roll your own harness.
1. It is cheaper.
2. You'll be forced to understand how the wiring works. Which is nice because then you'll know how to trouble shoot it if something breaks.

[mrein3]

To roll your own, look at stocker's picture.
Print it out.

The green wire from 87 on the high relay and the brown wire from 87 on the low relay are wires you need to make out of 10 or 12 gauge wire.
The red wire from the + side of the battery to the 30 on the relays you make WITH A SELF RESETTING CIRCUIT BREAKER protecting it from mishaps.

Before you start take your test light or volt meter out and mark the existing wires at the back of the headlights.
Turn on your low beams. See which wire has voltage and mark it "Low" with masking tape or similar. Also keep track of which position "Low" is in the plug.
Turn on your high beams. Mark that wire high. Note its position in the plug.

After wires and plugs are marked I like to take the plug off the headlight and remove the wire from the plug. That way I can reuse the plug. A small, flatblade screwdriver inserted in the connector will allow you to depress the little tang and pop the wire out.

The wire you marked "Low" goes to terminal 85 on the low relay. The wire you marked "high" goes to terminal 85 on the high relay.

Use Black colored 10 or 12 gauge wire and replace the grounds at the headlight plugs.

From NAPA get a couple of the correct connectors, part number 725147. This is the brass colored insert you pop out of the stock wiring plug at the headlight. Use these for 10 or 12 gauge wire you are making from the relay to the headlight. Also for the headlight side of the new ground wires you made. Make sure the wire from the "Low" relay goes to the position you marked "Low". Same for high.

Lesson learned:
I mounted the relays on the side of the truck that feeds the other side of the headlights. I used the stock wiring and stock connectors to terminal 85 on the relays. I didn't cut a single wire. One day driving down the road my lights started blinking between high and low beam. It turns out the wires that I didn't cut on the other side from the relays were vibrating together which caused voltage to alternate between the high and low relays. A couple pieces of electrical tape fixed that.

Long story short, if you do the relays the way I did you preserve the stock wiring for some future concours restoration, you now have a basic understanding of how the relays work, and you got some kick-butt light out of your headlights.

[Roadmarks]

@mrein3, I have to take issue with you when you say "you'll wonder why people waste their money on Hellas and other aftermarket lights." I'd have to say that Hella is one of the finest halogen lights in the world, along with Marchal and a couple of others. Hella is still OEM on Porsche, BMW, and Mercedes and many other high cars and trucks. Their driving and fog lights are fitted to the worlds winningist Rally cars. Hella lights are only a "waste" if you live someplace where you can't use them or they are poorly installed! Marchal lights are probably just as good but I don't like French products. My headlights are German made 7" Hella H-4s, and my driving lights are Hella 500s because I believe that they are the best in the world!

[Stocker]

Originally Posted by Roadmarks

@mrein3, I have to take issue with you when you say "you'll wonder why people waste their money on Hellas and other aftermarket lights." I'd have to say that Hella is one of the finest halogen lights in the world, along with Marchal and a couple of others. Hella is still OEM on Porsche, BMW, and Mercedes and many other high cars and trucks. Their driving and fog lights are fitted to the worlds winningist Rally cars. Hella lights are only a "waste" if you live someplace where you can't use them or they are poorly installed! Marchal lights are probably just as good but I don't like French products. My headlights are German made 7" Hella H-4s, and my driving lights are Hella 500s because I believe that they are the best in the world!

Well said.... the relay upgrade is a must on older vehicles like our trucks, and upgrading to E-codes is the next step up. IMHO, brand-name European lamps are superior to cheaper lamps.

Installing my first Marchals in the early 1970s was a real eye-opener (pun intended). Marchal apparently no longer exists, or at least is not available in the USA. Hellas are commonly available, great quality, and not overly expensive. Cibies are harder to find and costlier, but I prefer their beam pattern to Hellas.

[RPBurris]

I am with you Hatred...It makes my mind numb, but i am subscribed so i can figure this thing out. Great thread.

[DesertCat]

Originally Posted by BMERDOC

So I was looking over my truck for upgrades. Anything I can knock out quick and cheap. I looked into doing the headlamp relay upgrade to my truck so I measured voltage at the plug and found it to be .5v lower than system voltage. So am I correct to assume that its not a matter of voltage but its amperage where it counts?

Well, they are relative to each other, but yes assuming you can get full voltage to the lamps... current is the problem to be solved.

The fact that your voltage is low at the lamps means the path's resistance is too high (current is restricted and volts drop - Ohm's Law). This can be wire size, connector integrity, switch contacts and/or grounding. The voltage you read is the sum total of all this.

Others have chimed in here with suggestions of how... just thought I would answer the "why".

[BMERDOC]

Thanks for everyone's input! I just back from vaction and now have the time to look at some of the threads I was involved in before I left. I have several electrical projects to tackle so this is one of them that I'll put high on the list. I'll let ya'll know how it goes!!

[RossRinSD]

So I skipped reading a few posts, and gotta say the relay upgrades kinda suck. Every underhood relay I've installed (factory relays protected from water in the plastic boxes excluded) gets moisture in it, gets rusty, and stops working. Every one. I also picked up that made in China crappy yellow wiring harness with relays from LMC when I did the halogen conversion. I love the conversion. Wasted money on the harness. It wasn't long enough, and it was YELLOW.

But please, if you decide to do any conversion, use LOTS of zipties (and trim them) some split looming, and a little tape here. It kills me to see 14 inches of wire when 2 inches would do, wire nuts and masking tape, wires hanging all over...

[BMERDOC]

Originally Posted by RossRinSD

But please, if you decide to do any conversion, use LOTS of zipties (and trim them) some split looming, and a little tape here. It kills me to see 14 inches of wire when 2 inches would do, wire nuts and masking tape, wires hanging all over...

I always try make my harnesses look as good as factory!!

[ItsRandy]

Originally Posted by BMERDOC

Thanks for everyone's input! I just back from vaction and now have the time to look at some of the threads I was involved in before I left. I have several electrical projects to tackle so this is one of them that I'll put high on the list. I'll let ya'll know how it goes!!

VACATION? Who said you could go on VACATION? You have important work needing to be done on your baby...er, I mean...your truck. How could you go on vacation (grumble, grumble)?

[BMERDOC]

Originally Posted by ItsRandy

VACATION? Who said you could go on VACATION? You have important work needing to be done on your baby...er, I mean...your truck. How could you go on vacation (grumble, grumble)?

Wasn't my idea!! Believe me!! Mama said I had to go!!

[Stricklinator]

I bought the headlights and harness from LMC. The lights look good, but they are cheap plastic (I'll probably switch to a glass version later). The harness, made the job easier, but I had to add a few inches of wire to reach the driver's side headlight which is lame. I also had to use some black plastic loom to cover that ugly bright yellow loom.
Posted via Mobile Device

[RossRinSD]

Originally Posted by Stricklinator

I bought the headlights and harness from LMC. The lights look good, but they are cheap plastic (I'll probably switch to a glass version later). The harness, made the job easier, but I had to add a few inches of wire to reach the driver's side headlight which is lame. I also had to use some black plastic loom to cover that ugly bright yellow loom.
Posted via Mobile Device

I'm thinking of doing an HID conversion... I really like them on my other vehicles, but this is my closest to daily driven vehicle, I like to keep things low key and off the cop radar...

[BMERDOC]

To add to this discussion:A current thread dreadged up some old threads about headlights and I paid attention to the headlight suggestions on this thread. I am going to add either the Jeep headlights or the Sylvania Silverstars. I don't wanna run the risk of regret by buying some cheap headlights. Working now to lower my truck but when I do this upgrade I'll do one side first and leave the other stock to show the improvements because none of the threads I've found actually showed what improvements were made.

[Andy4639]

I've had mine in the truck for over a year with no problems. I wired them in myself and made my own connections. The lights are relays aren't the question here. It's the how to do it and why.

You want as much voltage and amps to the light that you can get from the battery and you don't want them dropping out in either one while driving.
So you add a straight wire that will carry the load of both the high beams being on from the battery to the relay. Then you use the old wires from the factory head lights to turn the relay on.
On a Chevy truck one relay per low/high beam light is enough. Once you have the relays in place the head light switch hardly see any amps and will last forever. You now have less load on the entire electrical system in the truck because of the relays. Your whole wiring system will thank you.
As for a GMC they are no differant except they have more connections.
2 relays will be enough.