Headlight fuse

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discussion starter · #1 · may 7, 2018

what size fuse should a headlight circuit have? they are on relays if that makes a difference.

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jimmy….is each headlight on a different fuse?

also, how many watts does each one draw?

the headlight relay circuit we have posted in the electrical section shows two 20 amp fuses….however, that may be overkill in some instances.

headlight fuse

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i used dave’s wiring diagram, also used 20 amp fuses, one for each of low beam and high beam on the relays, when i did my halogen conversion last year.

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fuses in a headlight circuit can be problematic if you blow a fuse your in the dark. circuit breakers will blink the lights on/off. your headlight switch has a circuit breaker in it from the factory for headlight function.

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fuses in a headlight circuit can be problematic if you blow a fuse your in the dark. circuit breakers will blink the lights on/off. your headlight switch has a circuit breaker in it from the factory for headlight function.

that’s why a dual fuse/relay circuit is recommended….one for low and one for high beam….also, when you upgrade, the new bulbs oftentimes will draw more current than the stock bulbs.

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if the relays are rated 30 amp use one 30 amp circuit breaker it can be used to power both relays, 30 amps x 12v = enough power for 360 watts of lighting.

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the circuit breaker in the headlight switch (which is for headlights only) will protect the switch if the wire(s) to relay terminal(s) #86 short.

everything else park/tail, brake, ip, interior, turn should be fused.

luck with your build.

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i don’t recall the factory ever putting a fuse on headlights.

acardon

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trifive automotive electrical wiring expert

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if the relays are rated 30 amp use one 30 amp circuit breaker it can be used to power both relays, 30 amps x 12v = enough power for 360 watts of lighting.

you missed davids point. circuit breakers are a good idea, but by having 2 fuses or cb’s, you can switch to the opposite beam and still have good lights instead of blinking lights.

ato automatic reset breakers are available so they can be used in the inline ato fuse holders. https://www.delcity.net/store/ato:atc-universal-blade!style/p_823686.h_198107

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i don’t recall the factory ever putting a fuse on headlights.

upgraded headlights will draw more amps than the stock factory 50 watt bulbs….the stock headlight switch was designed to handle the load of the original bulbs, not upgraded ones that draw more amps.

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according to the factory wiring diagram the headlights do not have fuses. there is a circuit breaker built into the headlamp switch. i added fuses and relay to mine when i went to aftermarket headlamps, but stock do not get fuses

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what size fuse should a headlight circuit have? they are on relays if that makes a difference.

are you talking about the fuse that feeds the headlight switch or the fuse(s) that feed the headlight relays?

what size wire is used going from battery power to the input of the headlight relays?

toby

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acardon

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trifive automotive electrical wiring expert

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are you talking about the fuse that feeds the headlight switch or the fuse(s) that feed the headlight relays?

what size wire is used going from battery power to the input of the headlight relays?

toby

the diagram in post #2 shows 12 gauge for the power wires.

from the switch to the relay can be 18 gauge stock wiring or larger.

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the diagram in post #2 shows 12 gauge for the power wires.

from the switch to the relay can be 18 gauge stock wiring or larger.

your right, i missed that. then 25 amp would be the appropriate fuse for that but the 20 amp will be fine since each h/l won’t draw more than that and it will protect the wire.

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Read more: Learning to drive? 12 car functions you need to know (+images)

you missed davids point. circuit breakers are a good idea, but by having 2 fuses or cb’s, you can switch to the opposite beam and still have good lights instead of blinking lights.

ato automatic reset breakers are available so they can be used in the inline ato fuse holders. https://www.delcity.net/store/ato:atc-universal-blade!style/p_823686.h_198107

i did not miss anything. industry standard for powering head lights is through circuit breakers. diy can do anything they want including a 1/4″ bolt in the fuse holder if desired.

1 circuit breaker is all that is required for 2 headlight relays only 1 relay works @ a time.

enjoyed the chat, live well.

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did he mention what type of headlight? bad eyes and a phone, maybe i missed it. a 20 amp fuse seems like a bit much unless he’s doing a headlight conversion and circuit upgrade.

mine is setup like david’s diagram, but i’m using a 60 watt sylvania headlight (h6024 if memory serves me correct). i could use a 20 amp fuse since i’m running 12 gauge wire and relays to support the amperage, but i won’t. i’ll likely use a two 10 amp (15 max) fuse — one for each relay.

i beefed up the headlight circuit for a future upgrade if i feel the need. at that time, i will increase the fuse size accordingly.

i definitely agree that two fuses or cbs is a good idea, especially if using a fuse.

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discussion starter · #16 · may 9, 2018

i have not been able to get back to this thread for a couple days and i thank you for the replies. i should have clarified that the vehicle in question in a jeep that i installed a chinese $50 ebay wiring harness in a couple months ago. there is a dedicated wire coming out of the fuse box for the headlight switch and that’s the one that keeps blowing. i do have relays on the headlights that have a 20 amp fuse in the power wire feeding them that is holding up fine. the headlight switch is a universal one. i am guessing that maybe i need to run a heavier wire and inline fuse to the headlight switch and just not use what’s in the fuse box. i don’t recall the size of the wire but it doesn’t look as heave as oem uses.

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discussion starter · #17 · may 9, 2018

headlight fuse

. here is the diagram i went by when installing the relays. like i said, that part has been solid.

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there is a dedicated wire coming out of the fuse box for the headlight switch and that’s the one that keeps blowing.

what is the size of the fuse that keeps blowing? shouldn’t take much, since the load is now running through the new 20 amp fuse….also, what does the rest of the circuit to the h/l switch look like?

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jimmy, if you have a separate power feed for the hl’s on the relay (#30), the only load on the hl “switch” is for the coil of the relay (# 85 or 86) when on, and any other loads on the hl sw., ie, parking lites, taillites, gauge lites, lic. plate lite, etc.

acardon

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trifive automotive electrical wiring expert

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jimmy, if you have a separate power feed for the hl’s on the relay (#30), the only load on the hl “switch” is for the coil of the relay (# 85 or 86) when on, and any other loads on the hl sw., ie, parking lites, taillites, gauge lites, lic. plate lite, etc.

and you could have a short on any of the other circuits that are on the headlight switch.

when you say the fuse keeps blowing, do you mean it blows as soon as the fuse is installed or after driving a while? in other words, is it intermittent or a solid short?

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Category: Headlights