[fiddlerpin]

What would be a good fuse size for the red wire circuit (original wire harness) on a 57 chevy. I would like to fuse it because they came without a fuse. I don't power my headlights from the headlight switch anymore (use relays and power them from the battery) and only use the cigarette lighter to plug in an IPod under 3 amps. Also was thinking of installing a master fuse for the pink circuit ahead of the smaller accessory fuses. Jim

 

[Rapper57]

I don't work in colors. I fuse to protect the wire first...now you'll get someone to answer your question faster! :sign0020:

 

[oldchey57]

Fuse

Since the factory didn't fuse it, it shouldn't be a problem, they didn't think it necessary. I would put in a inline fuse, probably 15A max.

Joe

 

[fiddlerpin]

Since the factory didn't fuse it, it shouldn't be a problem, they didn't think it necessary. I would put in a inline fuse, probably 15A max.

Joe

I think it should have been required. How many of these cars had electrical harness fires from the cigarette lighter shorting out. I know of several back in the day. Jim

 

[oldchey57]

Fuse

I think it should have been required. How many of these cars had electrical harness fires from the cigarette lighter shorting out. I know of several back in the day. Jim

I didn't design the car, I made a suggestion.

Joe

 

[Rapper57]

Fuse sizes for wire sizes...#12 (20A), #14 (15A), #16 (7.5A) those are Max fuse size to protect the wire from overheating. Of course you can always go smaller to protect a circuit. Another way to protect wire is with circuit breakers which can be reset if you have a one off issue you can clear.

Should have posted this the first time but I really thought someone would jump in as they usually do. :anim_25:

 

[oldchey57]

Fuse

Since the wire should be #14, I figured 15A max would do.

Joe

 

[fiddlerpin]

Understood Just saying. Thanks for the suggestion Joe

 

[Pops @ Tri-5.com]

Jim....I'd PM Don (Acardon) for a good answer....15Amps sure doesn't sound right to me for the load of your entire electrical system.

 

[fiddlerpin]

Good idea David. Or I could take an amp reading of that wire with all loads operating with and amp meter from work. As I said I don't think the load on that wire would be much with converting the headlights over to relays and maybe the radio (newer model)

 

[Pops @ Tri-5.com]

Jim....I'll go out on a limb here....I don't think using relays reduces the overall load seen by the battery...It just puts the load on different wires....Eventually the battery/alternator will see that load.

 

[acardon]

I think you'll find your using less than 15 amps on the red wire circuit, even with the lighter.
A 14 gauge wire will carry 30 amps for 10 feet with minimun voltage drop. ..... http://www.rbeelectronics.com/wtable.htm. The 3rd chart on that link considers allowable voltage drop (less than 2%), not melt down current. If you notice that 20 gauge wire is not even on the chart and our tri-5s are full of 20 gauge wires, even to the headlights which are on a 13 amp breaker in the light switch.
There are a lot of things that GM didn't fuse on older cars besides the cigrette lighter. Power windows, power seat, and windshield wiper motor was not fused. Some of these motors had internal circuit breakers, but that didn't help if the wire schaffed through the insulation under the dash.