The Stovebolt Site Forums The Shop Area The Electrical Bay Headlight relay - power wire

Right now my headlights are wired directly to my battery and operate via a switch I installed on dash (I got tired of chasing wires and just wired 'em directly).
Everything was fine for a while 'cept they weren't as bright as I'd like. A month or so ago, I noticed when I turn the light switch on, my amp gauge goes up.
I was given a headlight relay and wondered if this might cure what ails me. Both the brightness factor and amp problem.
Instead of wiring the relay directly to the battery, can I run the power wire into the firewall and tap into the power wire going to the dash switch I installed which is already wired directly to battery with inline fuse? So it'd be tapped in just upstream of the dash switch.
Or does this defeat the purpose of the relay?
Since I've already got one wire with inline fuse, I didn't want to do another one.

The amp meter is moving when you turn the headlights on because the headlights are using power (amps) and the guage is simply showing that usage. That in itself is not a problem.

If you lights are dim it is probably because either your switch or wire are too small to carry the required current (measured in amps) and therefore you have voltage drop which results in dim lights.

The purpose of a relay is to act as a remote switch. If the relay is big enough (capacity, not physical size) and your wire is also big enough the relay could solve your problem.

Are you headlights something other than stock? If so they may require more power than the stock switch and wiring will support.

What size wire are you using? What is the rating of the fuse you are using? What is the rating of the switch? And what is the rating of the relay?

You said it started a month ago? Did you change something in the wiring back then?

If you haven't made any wiring changes lately, the first thing I would check is your battery. They tend to crap out this time of year.

Well, well. While I was at work a couple hours ago, I was looking at my wiring and trying to make sense of the relay (your tax dollars hard at work - on my truck!).
I pulled the ground connection I made up at the original headlight junction by the horn relay to look for corrosion. Looked good so I hooked it back up. That was the only thing I disconnected and then re-seated. Got in to drive home, hit the light switch and the amp gauge barely moved. Was good all the way home. Guess maybe I need to clean the ground connection. Lights are still a little dim and always have been.
OldSub,
my headlights are stock and the wire that came with the switch is about 16-18 gauge. The fuse is a 15 amp.
Should I rewire with a 12 gauge for brighter lights and if so, would only the power wire to battery need to be changed to 12? Or should the wiring going out to headlights be changed as well?
Gord,
Seems like the battery's got plenty of juice and there's not much in the way of cold weather here. I've been away from cold weather so long I'd forgotten how it affects batteries though. Hey by the way, you had any Kilkenny lately? I've tried to find it here but, nobody's got it. If you ever happen to see Karl Strauss "Red Trolley Ale", pick it up. I think if you like Kilkenny, you'll like the Red Trolley.
-David

How about some new halogen bulbs?

OK, here's my suggestion:
Use a #12 or larger wire for ALL conductors. The headlights pull a considerable amount of amperage, and the smallest wire in the circuit is the choke point. It would be like supplying a fire truck with a garden hose, and expecting it to pump lots of water, if even one wire is smaller gauge. A 6-volt system needs heavier wire than a 12-volt.

The headlight relay is supposed to mount close to the lights, and shorten the path for the heavy current draw. The dash-mounted light switch just turns the relay on and off in that case, so the wires to the switch can be smaller without a problem. Make the wires to the relay from the battery, and from the relay to the lights heavy enough to carry plenty of current. ALL ground connections should be clean and tight, and should be attached to a a well-established ground, like a frame rail or engine/transmission part, not sheet metal.

Good luck!
Jerry

The ground connection ... so it was mother nature that made the wiring change.

I didn't forget about you living down in Margaritaville - just figured that days got shorter there too - means lights on longer - more work for the battery.

Had a friend visit recently from county Laois, Ireland. He lives nears Kilkenny. Went to the pub and had a few K's. Mmmmm...

Looks like Red Trolley is only available in your area for now:
Red Trolley

Cool. Got the plan and I'll give her a whirl. Let ya know what happens.
-David

Mugsy, Hotrod basically answered the question you asked me. His fire hose to garden hose comparison is good. From your description of what happened it sounds like the one connection was the problem, and likely will be again.

I think the poor connection was acting like a resistor, causing the current flow to go up, while also reducing the voltage and making the lights dim. Any time anything acts as a resister, whether its a poor connection, too small wire, a bad switch or an actual resister, amps will go up and voltage will go down.

15 amps seems small for a headlight circuit, but I don't have the actual current draw in my head.

Headlights are often protected by a circuit breaker because if they fail, its almost always going to be dark (otherwise you would not have turned them on) and if they don't come back on you could have an accident because you can no longer see.

I've heard arguments both ways as to whether that is a good idea...

A fuse or circuit breaker should be sized to protect the wire and switches in the circuit. The wire should be sized to provide full voltage at the needed current flow.

Heres a link to a wiring diagram for relay controlled headlights from www.6066gmctrucks.org. It's for duals but the principle is the same.

Mugsy,
I don't understand why your AMP gauge moves if your headlights are connected directly to the battery. In any case, if you have them connected with no fusing, one short and you could loose the whole truck in afire.

The standard sealed beam headlights that came from the factory will turn yellow & get dim with time, the more you use them the quicker that time comes.

The halogen type will burn white & brighter out of the box then a new old style sealed beam headlight, but they stay that way right up to the time they blow out.

Of course keeping the voltage at 12-14 volts at the light helps. You can test your wiring by checking the voltage at the headlight plug, if it's anything lowered than about 1-2 volts then the out put of the charging system you will want to check it out for corrosion, bad switch and connector. this is were the relay system help, instead of losing any of the voltage through the wiring (Voltage drop) you run power to the light through a shorter wiring with the relay system, getting less voltage drop, and brighter headlights.

There are a few WebPages on the net now with Headlight Relay Systems on them, my site even has one linked above. It's wired for the GMC Quad headlights, but just drop off two of the lights for most Chevy trucks.

Another good page of my website to have a look at is the General Wiring Tips page. I cover things like having good grounds & wire sizing just to name a few. Also you will find links to all the other Lighting/Wiring Project pages, which were done with 1960-66 GMC Trucks in mind, but most can be applyed to other & Older trucks as well.

truckernix, The amp gauge move UP because the lights are hooked the battery, and the power to charge the battery come from the alternator thru the amp gauge to the battery, so up is good because you are using more power from the battery so more power is need to fill it back up.

David: I saw the news tonight - snowing in Southern California! Maybe I wasn't so far off the mark. That's all I am going to say...

No sh!t!! It's bloody cold tonight. I might actually have to use the choke to start her up for the drive home!
I haven't yet hooked up the relay. Was gonna do it tonight at work but, had to do work that I'm actually paid to do.

Here's my headlights/relays project:
Wiring Headlights to Relays

Don't forget the dimmer switch. These things get pretty dirty inturnlly. You might want to clean or replace the dimmer switch. Just something not to overlook.

Got the relay installed finally. No go. Still a bit on the yellowy dim side. I changed my grounds to the frame and checked all my wiring. The relay is hooked directly to battery with inline fuse.
The lights being a little dim was not as much concern as my amperage increasing so much when the light switch was turned on. The amp problem seems good after cleaning up the ground connections.
One of these days I'll check the voltage at the light sockets and if good, I'll fork out the dough for some halogens I guess.
A guy at work said if everybody was driving around in '65 Chevy's, my lights would probably look normal.

Check the voltage on both high beam and low beam. And if you can borrow a halogen from someone check the voltage at the the halogen too.

With a volt meter and some time you can find exactly where the problem is by identifying where in the circuit the voltage drop is occuring.

The power feed for the headlight relay should be the hot wire on the alternator . this way full charging/battery current will always be supplied to the headlights and they'll be nice & bright all the time .

I'm surprised Hotrod didn't mention this as he's obvoisuly sharp on 'lektrikery .

I've never seen an add on typ headlight relay that didn't contain fuse or CB .

NAPA sells nice ones , they used to sell 6 volt ones too , sigh .

Of course you know to smear bearing grease on the ground wires you cleaned up.....