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Old 12-21-2010, 04:23 PM
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High beam low beam relays

Just a quick question and I haven't found an answer... I'm rewiring the relays to my headlights. I noticed the 12 GA hot wire coming from the battery goes to one relay (low beam) and piggy backs over to the other relay (High beams) Is it better to have a separate feed wire from the battery to each relay, rather than picking up the hot wire from the one relay? or does it matter?

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Old 12-21-2010, 04:58 PM
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The answer is......it depends

If your vehicle is setup so that when you switch to High Beams, your Low Beam lights go out, then its OK to piggyback the power from relay to relay, because only one relay at a time is requiring power for the headlights.

However, it you had four headlights, two low beam and two high beam, and both sets are "On" when you select the high beam switch, then I would have separate power wires to each relay as a safety measure.
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Old 12-21-2010, 05:24 PM
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Quote:
Originally Posted by Hoptup32
The answer is......it depends

If your vehicle is setup so that when you switch to High Beams, your Low Beam lights go out, then its OK to piggyback the power from relay to relay, because only one relay at a time is requiring power for the headlights.

However, it you had four headlights, two low beam and two high beam, and both sets are "On" when you select the high beam switch, then I would have separate power wires to each relay as a safety measure.
I appreciate it. Wasn't sure... I checked the wiring and when I depress the high beam switch, the low beams power turns off. I'll just redo it with the piggy back. Was thinking I might lose power going from one relay to the other using the one power source.
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Old 12-21-2010, 06:36 PM
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Quote:
Originally Posted by Hoptup32
The answer is......it depends

If your vehicle is setup so that when you switch to High Beams, your Low Beam lights go out, then its OK to piggyback the power from relay to relay, because only one relay at a time is requiring power for the headlights.

However, it you had four headlights, two low beam and two high beam, and both sets are "On" when you select the high beam switch, then I would have separate power wires to each relay as a safety measure.
only one circuit is used at a time----even on 4 lamp systems, the low beam circuit shuts off.

Now, it may be a good idea to run separate lines to each relay, or install a junction with 2 circuit breakers or fuses----1 for each relay.
This would insure that if a fuse or breaker pops on one of the circuits----the other will still work.
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Old 12-21-2010, 07:07 PM
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The optimum way would be to run separate fused power feeds to each relay. If one fuse blows for whatever reason you would still have access to lights, either lo or hi depending on which fuse is out.

Vince
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Old 12-21-2010, 08:06 PM
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Quote:
Originally Posted by Bryan59EC
only one circuit is used at a time----even on 4 lamp systems, the low beam circuit shuts off.

.
Not always, I know many 4 headlight systems that the low beams run on a low filament in one light each side on low beam and a high filament in that same light on high beam(dual filament), along with the second light only being high beam(single filament.

Mid to late 60's GM 4 headlight systems come to mind, they are 2 high/lows and 2 highs. I've had several friends have me wire dual relays, and they then switch to 4 lights both having high/low(dual filaments), they want even more light at night.
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Old 12-21-2010, 08:13 PM
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I agree with Vince..
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Old 12-22-2010, 04:35 AM
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If the avatar pic is the vehicle..... seperate pwr feeds are redundant IMO ..... with a two light sys (hi-low) if the fuse/circuit popped and I'd want to sort out what made it short out and avoid possible meltdown.
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Old 12-22-2010, 05:32 AM
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Quote:
Originally Posted by ericnova72
Not always, I know many 4 headlight systems that the low beams run on a low filament in one light each side on low beam and a high filament in that same light on high beam(dual filament), along with the second light only being high beam(single filament.

Mid to late 60's GM 4 headlight systems come to mind, they are 2 high/lows and 2 highs. I've had several friends have me wire dual relays, and they then switch to 4 lights both having high/low(dual filaments), they want even more light at night.

Still----only ONE circuit at a time----Low or High----that is all the dimmer switch will allow-----as for more lighting on these, just upgrade to Halogen sealed beams---------anything more than that and it annoys oncoming traffic.

I frankly don't care how far one wants to see at night, but if the ONLY thing I see is that bozo with lights brighter than the sun---it becomes an unsafe situation for everyone on the hiway.
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Old 12-22-2010, 08:33 AM
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Quote:
Originally Posted by Bryan59EC
Still----only ONE circuit at a time----Low or High----that is all the dimmer switch will allow-----as for more lighting on these, just upgrade to Halogen sealed beams---------anything more than that and it annoys oncoming traffic.

I frankly don't care how far one wants to see at night, but if the ONLY thing I see is that bozo with lights brighter than the sun---it becomes an unsafe situation for everyone on the hiway.
Bryan, I understand your frustration with bright lights. I'm not installing relays to brighten the headlights plus I'm also already running halogen sealed beams. My reason is to reduce amperage drop and avoid overheating my headlight switch which tends to get hot after running with the headlights on. Plus I constant hear that it's better to run relays on the headlights rather than not... I figure, if I don't like the relays, not much is lost, I can always go back and remove them. I have a 2 fuse block on my firewall which is not being used. I'm thinking about running the 12GA wire from the battery to that fuse block with one wire, then splitting it to each fuse and using that to power the relays. This way, I eliminate running another 12GA wire through my firewall and if I blow a fuse... I still have the other fuse (hopefully) to still have lights. I think this will work well. I appreciate everyones advice because I hate doing things twice.
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Old 12-22-2010, 01:59 PM
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Just finished up installing the relays. Took a while because I routed the wiring nicely and made nice connections. I used the harness on the relays which made the job easier and neater as well. The relays work without any wires smoking... or fuses blowing The lights appear to be about the same perhaps a little brighter than normal. I started my truck and the voltmeter went to 14.1 volts without the lights on. I turned the lights on and the voltmeter barely moved, maybe .2 volts if that . I also turned the high beams on and didn't get much more on voltage drop. Without the relays, my voltage with the lights on would drop to about 12.5- 13.0 volts. So I'm real happy I did this even though I'm only using sealed beam halogens, and definitely recommend to others using the relays. Thanks to everyone who provided me with a wiring diagram and info...
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Old 12-22-2010, 03:16 PM
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Bryan, after I thought it through again you are right, it doesn't run both filaments at the same time in a bulb, it shuts off the low and turns on the high.
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Old 12-22-2010, 04:05 PM
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Quote:
Originally Posted by kleen56
Bryan, I understand your frustration with bright lights. I'm not installing relays to brighten the headlights plus I'm also already running halogen sealed beams. My reason is to reduce amperage drop and avoid overheating my headlight switch which tends to get hot after running with the headlights on. Plus I constant hear that it's better to run relays on the headlights rather than not... I figure, if I don't like the relays, not much is lost, I can always go back and remove them. I have a 2 fuse block on my firewall which is not being used. I'm thinking about running the 12GA wire from the battery to that fuse block with one wire, then splitting it to each fuse and using that to power the relays. This way, I eliminate running another 12GA wire through my firewall and if I blow a fuse... I still have the other fuse (hopefully) to still have lights. I think this will work well. I appreciate everyones advice because I hate doing things twice.

This is the better way to have it.. Good to hear it is working better..

I just did a Coupe that had One fuse running two relays.. Not good.. One was his Elect fan, And the other was for a elect motor to open and close his cowl vent.. Not good at all.. The wires was burnt when I took them out.. The fuse was burnt inside the fuse holder.. Now It's done right.. Good luck..

Last edited by NEW INTERIORS; 12-22-2010 at 04:10 PM.
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Old 12-22-2010, 05:01 PM
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Quote:
Originally Posted by Bryan59EC
Still----only ONE circuit at a time----Low or High----that is all the dimmer switch will allow

If you are referring to the relay wiring the only load that runs through both the headlamp switch and the dimmer switch is the coil or coils of the relay or relays. A typical 12 volt relay coil pulls about 300ma, two relay coils on at the same time would be 600ma, far less than if all headlamps were on and running though the headlamp switch and dimmer switch.

Vince
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Old 12-22-2010, 05:41 PM
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Good to hear you got it worked out.
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