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Old 04-22-2009, 10:46 PM
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Relays on headlights

I'm not running any relays on my headlight and noticed that when I turn the headlights on, my volt gauge drops to 10 volts. With the lights off, I'm at 14.1 volts. I'm using 12 gauge wire to the headlights. The headlights appear bright and I'm using the standard Halogen round bulbs. Should I install relays on the Low and High beams? The wiring is simple but I have a question on the Hot wire coming from the battery. Is it possible to run one wire from the battery to the relay and then jump from the #30 terminal on the relay to the other relay on the High beam relay. That would eliminate running two separate wires to each relay. Or should I just run the headlights the way they are and forget it? Any tips on doing this install is appreciated.

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Old 04-22-2009, 10:59 PM
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Relays

Relays are your best friend. They take small control amperage to run big draw amperage. If you you run relays, your alternator will charge only when needed and not burn out by constantly running when lights are on. (my opinion)
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Old 04-22-2009, 11:32 PM
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Quote:
Originally Posted by fishstallion
Relays are your best friend. They take small control amperage to run big draw amperage. If you you run relays, your alternator will charge only when needed and not burn out by constantly running when lights are on. (my opinion)
And they will also be brighter! Check out the Doc Vette archives for the best ways to wire them up,He was everyones HERO when it came to wiring,I know He was mine!
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Old 04-22-2009, 11:37 PM
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Jeff, where do I find the Doc Vette archives at? I couldn't find anything on a search? Thanks for the info guys.
Ed
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Old 04-23-2009, 12:15 AM
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Yes you can jump the two relays with a single main power. I have done this on dual cooling fan relays. It's your 'trigger' power, such as, your headlight switch, or your high beam switch, that will activate your different relays. On the relay pigtails I have, the '30' is a 10 gauge wire.
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Old 04-23-2009, 01:36 AM
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well if the engine is not running and you have this voltage drop when you turn on the lights then this is normal and to be expected.

now if its doing this voltage drop with the alternator charging then i'd be looking into a resistance issue or charging issue, etc.

to me a relay is just a heavy duty switch to handle higher amp loads, instead of using little switches that arent designed to control higher amperage/wattage

but then i am far from an electrician and have never actually converted to, or wired in, a relay for anything, ever, because well theres too many wires and ive also never taken the time to study how they work. they just magically work. i dont know lol.



good luck
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Old 04-23-2009, 07:34 AM
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Headlamps are a high amperage draw, you will see some voltage drop when you turn them on regardless if they are on relays or not. When you turn them on is the engine idling? Some alternators do not charge until the RPM is above 1000.

Vince
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Old 04-23-2009, 08:56 AM
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Vince, the engine is idling. I'm running a GM one wire alternator (I believe 110 volt?) At idle without the headlights, I'm at 13.5 volts. When it's cold, the alternator is not charging at all until I rev it a bit, then the volt meter jumps back up to 13.5 and even 14.1. When the lights come, The voltmeter at idle is about 10. Idling at a red light with the lights on, and the turn signal on and foot on the brake, The voltmeter needle is jumping around 8 volts and sometimes 7 volts, which gives me some concern.
Ed
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Old 04-23-2009, 08:59 AM
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Yes, you should run relays. First of all, it might save the headlight switch, or - maybe even the car

As far as relays are concerned, they are a bit confusing so if you haven't worked with them before, take some time to study up. Here's a good web site:http://www.madelectrical.com/electri...dlights2.shtml. He is trying to sell his "kits", but actually has a good enough write up to wire the lights.

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Old 04-23-2009, 09:31 AM
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Quote:
Originally Posted by kleen56
Vince, the engine is idling. I'm running a GM one wire alternator (I believe 110 volt?)
And here's the problem. Most one-wire alternators don't charge at idle. Frankly, I've never understood the attraction of the one-wire since it has these limitations. And it's 110 AMP. If it were 110 volt you'd have house current.

As for the relays, they won't change the voltage drop unless your headlight wiring is very small diameter. The majority of the resistance is in the headlight filament, so a relay will have little effect on the measured voltage drop. The factory didn't need them.
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Old 04-23-2009, 09:57 AM
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Quote:
Originally Posted by joe_padavano
And here's the problem. Most one-wire alternators don't charge at idle. Frankly, I've never understood the attraction of the one-wire since it has these limitations. And it's 110 AMP. If it were 110 volt you'd have house current.

As for the relays, they won't change the voltage drop unless your headlight wiring is very small diameter. The majority of the resistance is in the headlight filament, so a relay will have little effect on the measured voltage drop. The factory didn't need them.
Joe, I apologize, I'm not an electrician nor claim to be one. However, I appreciate you correcting that for me. I do have a 110 AMP alternator. Reason for going with the one wire, was simplicity and clearing all that wiring I had going to the voltage regulator which is no longer needed. Thanks. Ed
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Old 04-23-2009, 10:09 AM
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Simplicity is ALL a 1-wire alternator has going for it.

It's no selling point, as far as I'm concerned- to wire it "correctly" doesn't cause any undue complication or unsightliness, IMHO.

More HERE.
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Old 04-23-2009, 10:32 AM
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Here's a site that you can go to to get wiring diagrams and helpful information on relays for the headlight system:

http://dsl.torque.net/images/Relays.pdf
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Old 04-23-2009, 05:01 PM
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Relays will not solve your issues. The purpose of the relay is to take the load off of the switch and put it on the relay contacts. This allows lighter switches to be used to control heavy loads. Your issue is your alternator is not able to keep up with the load of the headlights. You need to fix that first.
Have the charging current checked to see how well the alternator is working.
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Old 04-23-2009, 08:29 PM
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Quote:
Originally Posted by T-bucket23
Relays will not solve your issues. The purpose of the relay is to take the load off of the switch and put it on the relay contacts. This allows lighter switches to be used to control heavy loads. Your issue is your alternator is not able to keep up with the load of the headlights. You need to fix that first.
Have the charging current checked to see how well the alternator is working.
Not sure if this question make sense T bucket, but the alternator I have has a consistant 14.1 volts or charge with the engine running and no drain on the system. I have a voltmeter connected to read the readings from my dash. Are you referring to a check of how many AMPS are coming from the alternator? Any suggestion on what may be wrong with the alternator and what method can be use to check it, or to look for?
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