fuse/circuit breaker

Dave Sherburne NY · Jan 21, 2012

I'm rewiring the lights in a 6 volt 1929 Essex. Can I replace the fuse with a 12 volt Circuit Breaker? There are 2 headlights and 2 taillights on the circuit. Parking lights and signal lights are a separate circuit . What amperage breaker should I use??

John in Nebraska · Jan 21, 2012

Since fuses react to Amps not volts, I don't see a problem here. I would try a 20amp fuse, if it blows, go from there, then get a circuit breaker of the size that works. Much better than burning down a nice old car.

Rob NC · Jan 21, 2012

I would try to keep it as original as possible.

buickanddeere · Jan 21, 2012

A properly selected fuse provides better protection than a breaker.
Convenience is something else but.........there should not be multiple repeating faults.

Anonymous-0 · Jan 21, 2012

Everyone is right. As buickanddeere states a fuse is a better choice than a circuit breaker and multiple failures means there is a problem. Circuit breakers or fuses "open" because of current flow (amp rating) not voltage. So to figure fuse size you need to know the power consumption of your lights in watts divided by the voltage which gives you the current flow or amps for the fuse.

Eric in IL · Jan 21, 2012

I thought fuse/breaker size was determined by wire gauge downstream from fuse location.

Anonymous-0 · Jan 21, 2012

That's correct Eric, you find the load (watts) you are trying to feed, size the wire accordingly so the fuse is the weak point by design.

big fred · Jan 21, 2012

Kinda depends on the application. In an airplane, a breaker is preferred, because it can be reset easily in flight. In a naval ship, a breaker is also used, and is backed up with a battle short for those times when you're taking fire and your life can depend on an overloaded circuit. Battle short is used to bypass circuit protection devices. But yeah, in a passenger car, a fuse is preferred over a breaker. Exceptions in the case of switching breakers in lieu of switches.

Jon Hagen · Jan 22, 2012

I would use two automatic reset breakers, or a breaker for the headlights and a fuse for the tail lights a 15-20 amp for the headlights and a 7-10 amp for the taillights. A measurement of the actual amp drain of the head or tail lights would help properly size the breakers / breaker and fuse.

A momentary short will blow either a fuse or breaker, but with a blown fuse, the lights will stay out. With an auto reset breaker, there is a better than even chance that the breaker will reset ang get the lights back on so you have some light to stop the car.
All cars have used an auto reset breaker on the headlight circuit since the early 50's

Put the tail lights on a smaller fuse, about 1/2 that of the headlight breaker, so a short in the tail lights will not also knock out the headlights

36 Coupe · Jan 22, 2012

Ford used a 20 amp fuse in 1936,auto reset in 1939. I favor the fuse.A reset circuit breaker will keep trying to close on a short circuit.That can weld the contacts.I would put a dual headlite relay on the car.The relay will have its own fuse and it takes the high current off the headlite switch.Makes for brighter lites on the old cars.

John T · Jan 22, 2012

While either will work and both have advantages and disadvantages, since its an antique auto Id use a fuse instead of a circuit breaker.

To size the fuse and circuit wiring gauge you

FIRST determine the total actual load CURRENT by adding all the lights total wattage and divide by the voltage Watts = Volts x Amps and Amps = Watts/Volts

SECOND you determine the necessary wire gauge, as an example Id use 12 gauge if the continuous load was say 16 amps,,,14 gauge if the continuous load was like 12 amps etc but I wouldnt go less then 14 gauge regardless

THIRD size the fuze to protect the wire (its amp rating) as an example if the wire is rated for 20 amps you can use a 20 amp fuze, if the wire is rated for 15 amps use a 15 amp fuse etc

YOU DETERMINE THE LOAD,,,,,,,,SELECT THE WIRE TO HANDLE A CONTINUOUS LOAD (I use an 80% safety factor i.e. if the wire is rated 20 amps I dont like more then a 16 amp continuous load) THEN SELCT THE FUSE SIZE TO PROTECT THE WIRING

As a pure guess youre probably lookng at 12 gauge wire and a 20 amp fuze or 14 gauge wire fused at 15

John T

John T · Jan 22, 2012

While either will work and both have advantages and disadvantages, since its an antique auto Id use a fuse instead of a circuit breaker.

To size the fuse and circuit wiring gauge you

FIRST determine the total actual load CURRENT by adding all the lights total wattage and divide by the voltage Watts = Volts x Amps and Amps = Watts/Volts

SECOND you determine the necessary wire gauge, as an example Id use 12 gauge if the continuous load was say 16 amps,,,14 gauge if the continuous load was like 12 amps etc but I wouldnt go less then 14 gauge regardless

THIRD size the fuze to protect the wire (its amp rating) as an example if the wire is rated for 20 amps you can use a 20 amp fuze, if the wire is rated for 15 amps use a 15 amp fuse etc

YOU DETERMINE THE LOAD,,,,,,,,SELECT THE WIRE TO HANDLE A CONTINUOUS LOAD (I use an 80% safety factor i.e. if the wire is rated 20 amps I dont like more then a 16 amp continuous load) THEN SELCT THE FUSE SIZE TO PROTECT THE WIRING

As a pure guess youre probably lookng at 12 gauge wire and a 20 amp fuze or 14 gauge wire fused at 15

John T

fuse/circuit breaker

Dave Sherburne NY

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John in Nebraska

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Rob NC

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buickanddeere

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Anonymous-0

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Eric in IL

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Anonymous-0

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big fred

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Jon Hagen

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36 Coupe

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John T

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John T

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