'40 Headlight circuit breaker amps

[russcc]

I have probably seen the amp rating for the stock '40 headlight circuit breaker somewhere, but can't seem to locate it. Can someone help me out with the correct amperage rating. Thank you.

[Zeke3]

I think it is 30 amps. It replaced a 30 amp fuse that was used on earlier models.

[Ken hash]

The total number of watts including headlights and tail lights divided by 6v should equal your amp draw. Good luck

[JSeery]

I know when they went to two circuit breaker one was 15A and the other 30A (the headlight circuit). So would guess that the single one would be 30A.

[russcc]

I switched to 12 volts, and am changing the deteriorated under dash wiring in the '40. Using a fuse block for the new under dash wiring. The reason I asked the question is so I can source the correct amp breaker for the headlight circuit. I have the rest of it covered. I was guessing if the headlights were originally 30A for 6 volts, then 15A for 12 volts should do it. ?

[Zeke3]

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The purpose of a fuse or circuit breaker is to protect the wiring. A rule of thumb that I learned during working on a Big Three production vehicle installation is that the wire size should be two sizes larger than the rating of the circuit protection used. For instance, if the fuse or circuit breaker is sized to carry enough current for 16 gauge wire (~22 amps), the circuit should be wired with 12 gauge to be adequately protected.

The posting above gives guidance on determining the current draw based on the wattage of your lamps.

Rule #1, don't let the smoke out.

[hotrodart]

Originally Posted by russcc

I switched to 12 volts, and am changing the deteriorated under dash wiring in the '40. Using a fuse block for the new under dash wiring. The reason I asked the question is so I can source the correct amp breaker for the headlight circuit. I have the rest of it covered. I was guessing if the headlights were originally 30A for 6 volts, then 15A for 12 volts should do it. ?

You might want to check the wattage of your 12 volt headlights (should be listed on the boxes). Remember that amps=watts/volts.....to size your fuses/breakers. Usually the fuse or breaker will be 120% of the steady state loads.