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Old 01-23-2019, 11:33 PM   #1
SunSoaked
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Relay mod 4 headlights- circuit breaker?

I'm in process of putting the headlights on relays. I'm pretty sure the factory has a circuit breaker in the circuit. So is this feature lost in the conversion? It would only be protecting the low power control wires to the relays. Should I add breakers on the load side of the relays? Seems goofy since the relays are within a foot of the battery now.
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Old 01-24-2019, 10:46 PM   #2
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Thumbs up Re: Relay mod 4 headlights- circuit breaker?

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I'm in process of putting the headlights on relays. I'm pretty sure the factory has a circuit breaker in the circuit. So is this feature lost in the conversion? It would only be protecting the low power control wires to the relays. Should I add breakers on the load side of the relays? Seems goofy since the relays are within a foot of the battery now.

If you tied into the main wire at the battery past the fender mount you have the fusable link in the wire already but if you tied straight to the battery I'd put a 40 amp breaker in line.
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Old 01-25-2019, 02:52 AM   #3
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Re: Relay mod 4 headlights- circuit breaker?

Here's two diagrams to help you out.

The first doesn't give a value but a 20 to 30 amp fuse or circuit breaker in each circuit should be plenty.

The second shows a 20 amp fuse.



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Using the Oms law calculator, if you are pushing 100 watts per headlight at 14 volts, you will have 9.8 amps in each light, so double that is 20 amps for the circuit. If you used a 30 amp fuse in each circuit you would be safe.




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Old 01-25-2019, 09:55 AM   #4
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Re: Relay mod 4 headlights- circuit breaker?

As always, thanks VetteVet!
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Old 01-25-2019, 01:07 PM   #5
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Re: Relay mod 4 headlights- circuit breaker?

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As always, thanks VetteVet!
You're welcome but I just illustrated what Andy said.
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Old 01-25-2019, 01:15 PM   #6
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Re: Relay mod 4 headlights- circuit breaker?

I wired it just like the 2nd diagram except I used 16 guage fusible link instead of fuses. Funny how Napa sells fusible links with a ring terminal for $7 or you can buy a spool of link for a dollar more. Lol
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Old 02-05-2019, 03:50 PM   #7
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Re: Relay mod 4 headlights- circuit breaker?

On that second diagram, wouldn't you rather consider using circuit breakers instead of fuses for safety purposes? At least if an overload occurs you won't completely lose your lights.
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Old 02-05-2019, 05:09 PM   #8
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Re: Relay mod 4 headlights- circuit breaker?

The breaker is in the light switch. After the mod, it only controls the relays. The hi/low are now on separate circuits. If one shorts, just hit the dimmer switch. I used fusible link cause it's more reliable and less clutter.
The difference is night and day I might add with the H4 bulbs and relay mod.
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Old 02-05-2019, 06:11 PM   #9
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Re: Relay mod 4 headlights- circuit breaker?

Here is how I have wired them in the past. Getting ready to wire my truck this way as well. I put a 30A fuse/breaker on the power feed. Wiring this way will not allow the low and hi to be on at the same time.

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Old 03-04-2019, 11:41 AM   #10
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Re: Relay mod 4 headlights- circuit breaker?

Is this for a GMC ? Thanks
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Old 03-05-2019, 09:34 AM   #11
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Re: Relay mod 4 headlights- circuit breaker?

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Is this for a GMC ? Thanks
Uhhhhhh....no.
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Old 03-06-2019, 01:08 AM   #12
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Re: Relay mod 4 headlights- circuit breaker?

On a 4-headlight system all you do is run extra wires to power the inboard high beam lights in parallel to the high beam filament on the outboard hi/lo beam bulb. So the relay wiring is the same if you have wired the bulbs together.
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Old 03-06-2019, 11:41 AM   #13
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Re: Relay mod 4 headlights- circuit breaker?

Thanks for the info . I just miss read the question when it was posted.
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Old 03-09-2019, 08:50 PM   #14
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Re: Relay mod 4 headlights- circuit breaker?

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Old 03-09-2019, 09:26 PM   #15
beaterku
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Re: Relay mod 4 headlights- circuit breaker?

I used the wiring diagram above to wire up my hi/low relays. One feed wire running to a 30amp fuse. You can see the heavy red wire jumping from one relay to the other.
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Old 03-10-2019, 01:35 AM   #16
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Re: Relay mod 4 headlights- circuit breaker?

beaterku that is some really neat wiring. Better than factory.
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Old 03-10-2019, 09:02 AM   #17
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Re: Relay mod 4 headlights- circuit breaker?

Could fused relays work? https://www.ebay.com/itm/12V-DC-40-3...MAAOSwuLFZw09j
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Old 03-10-2019, 03:05 PM   #18
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Re: Relay mod 4 headlights- circuit breaker?

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beaterku that is some really neat wiring. Better than factory.
Thanks. I am a bit anal retentive. I also have 3 relays on the pass side for fans and fuel pump.
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