Fuses

[captain marty]

Finished running new wiring to head and tail lights on my 28 AA and am in process of determing what amp fuses to use. I'm not an electrician but it can't be rocket science. Any help would be great.
Marty

[Tom Wesenberg]

20 amps should do fine.

You say "fuses", are you using more than one? If so you may want 10 amps for the horn and coil and 15 amps for the lights.

[Jim/GA]

6 volts or 12 volts? A 12 volt system uses half the amps for the same light output.

[steve s]

I think that the main principle to keep in mind is that the real role of the fuse is to protect the WIRING from overheating such that its insulation catches on fire and lights the car. Tables can be googled showing max amps for different gauge wires. Such data are approximate, depending also on the quality of insulation and available cooling air circulation. Of course, the fuse has to pass enough current to power the designated load.

Another principle is that amperage (current) capacity is what really matters, not voltage. However, as Jim points out, 6 volt wiring must be able to handle twice the current as 12 volt wiring in order to accomplish the same work. So, if you're still using your original 6 V wiring with you 12 V setup, you've got a nice margin of error, assuming it's in good shape.

Another consideration is whether you want to fuse your ignition circuit separate from other stuff--this is an argument against the very popular single fuse bracket sold by all the vendors for attachment beside the starter switch. If that fuse blows for any reason--like, say when you hit the horn and brake lights simultaneously in the middle of an intersection or other excitement--the engine will die and you're dead in the water.

Steve

[Mike V. Florida]

Originally Posted by steve s

If that fuse blows for any reason--like, say when you hit the horn and brake lights simultaneously in the middle of an intersection or other excitement--the engine will die and you're dead in the water.

Steve

Resetable circuit breaker that fits in the Fuse holder. Wait a few seconds and your ready to go!

[steve s]

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Originally Posted by Mike V. Florida

Resetable circuit breaker that fits in the Fuse holder. Wait a few seconds and your ready to go!

That's fine if you can stay calm and collected at such times, and all of the traffic around you likewise. Of course, if you've got a real short rather than a temporary overload, the breaker is not going to reset for any useful duration.

Actually, I've been using such fuse for over 15 years with no problems--all of my other wiring is brand new. But, I'm now convinced it's asking for trouble, and intend to swap it out as soon as my garage warms up. I've got lots of other fuses for the individual circuits, so only the wire from the starter switch/junction box/ammeter to my separate fuse block will be unprotected--maybe that makes the ammeter the fuse equivalent.

Steve

[P.S.]

I use a 40 amp between the alt and battery, everything else has its own fuse. Light get a 30 A, horn gets a 10, interior lights have a 5, ignition gets a 15.

I did that "whole car went dead" thing with the mono-fuse ONCE. Never again. Never.

[Christoph]

Never again with mono-fuse.

Going uphill over an intersection to the left, the engine died...

What i use now:
- one (the strongest ) as "Central" on the starter (i use 25 there)
- one to the lights (used to be my prob)
- one to the horn and
- one to the brake-light (as the switch might be a pain)

I do not need a ignition-fuse as this is covered by the central one ...

Greetings
Christoph


@ P.S.
I have a smaller (central-) fuse on the starter, than you use just for lights.
Not really a need, but i recommend to try smaller ones.

BTW
Good idea to protect interior lights separately (which goes along with my flash-lights)

[P.S.]

Originally Posted by Christoph

Never again with mono-fuse.

Going uphill over an intersection to the left, the engine died...

What i use now:
- one (the strongest ) as "Central" on the starter (i use 25 there)
- one to the lights (used to be my prob)
- one to the horn and
- one to the brake-light (as the switch might be a pain)

I do not need a ignition-fuse as this is covered by the central one ...

Greetings
Christoph


@ P.S.
I have a smaller (central-) fuse on the starter, than you use just for lights.
Not really a need, but i recommend to try smaller ones.

BTW
Good idea to protect interior lights separately (which goes along with my flash-lights)

I'm running halogens, and their inrush current dictates a larger fuse. Their current drain once on is around 20 amps for all (headlights, tail lights). But, getting the filaments from dead cold to full hot takes about 50 amps for about 5 milliseconds. The blow slope current curve of the 20 amp fuse shows that switching from high to low beam a few times would take the fuse. So, I upsized based on the 30 amp fuse blow slope.

I use a 40 amp between the battery and alternator because the 60 amp alternator can do 40 amps on really cold mornings for a few seconds after it kicks in. It settles to under 5 amps pretty quickly, but wanted to fuse for the wire size in this case. My whole car is wired with 10 ga. rubber and cloth covered wire of the appropriate Ford color scheme (it all matches the Model A wire color chart). It's just a LOT bigger, and everything is soldered and sealed. No exposed copper anywhere.

[steve s]

Originally Posted by P.S.

... My whole car is wired with 10 ga. rubber and cloth covered wire of the appropriate Ford color scheme (it all matches the Model A wire color chart). It's just a LOT bigger, and everything is soldered and sealed. No exposed copper anywhere.

wow!

[captain marty]

I am planning on running fuses for each area such as one for low beam headlights, one for bright, one for tail and one for brake lights. My system is original 6V. I've searched for candle power to watts but find there is no conversion. I am running 14 G wiring to all lights.
Thanks,
Marty

[P.S.]

Marty- There's no need to run a separate fuse for each filament of each headlight. One fuse for the lights is plenty sufficient.

Steve- Yep, you know it. That's how we electrical engineers roll... Just don't ask me about anything internal to the motor.. If the motor breaks, that's an automatic checkbook repair.

[steve s]

Originally Posted by captain marty

... I've searched for candle power to watts but find there is no conversion. I am running 14 G wiring to all lights.
Thanks,
Marty

There is no simple conversion. It depends on the efficiency of the particular light source for converting electricity to light and to a lesser extent on the color of the light. Why not just notice the current draw on the car's ammeter when you turn the load on? Our ammeters are notoriously inaccurate, but they're good enough for this purpose. Just allow a margin and don't go over the ~30 amp rating for non-bundled 14 gauge wire. OR, just follow P.S.'s recommendations.

I would suggest using heavier gauge for the main power line coming out of the alternator or cutout.

[P.S.]

Originally Posted by steve s

Our ammeters are notoriously inaccurate

Which is really sad when it only takes a minute or two and you can calibrate one of them to be very accurate. +/- 10% is easily achieved, but you can get them even closer than that if you work at it a little.

Originally Posted by steve s

I would suggest using heavier gauge for the main power line coming out of the alternator or cutout.

Absolutely!!!

[JBill]

Originally Posted by Mike V. Florida

Resetable circuit breaker that fits in the Fuse holder. Wait a few seconds and your ready to go!

Do you mean like the fuse holder on the starter or an in line fuse holder? And, where do you get that, and is it available for six volt system? Thanks!

[CarlG]

On my 92 Explorer, the circuit that feeds the turn signals kept blowing fuses. I couldn't find the fault, the shop that does some of my work couldn't find it either. Just kept on randomly blowing the fuse. So I put in one of the circuit breakers that plug in like a fuse and it's been going for over 5 years now. I'm never aware of when or if it actually is breaking and resetting, but I still have turn signals!

[BILL WILLIAMSON]

Originally Posted by JBill

Do you mean like the fuse holder on the starter or an in line fuse holder? And, where do you get that, and is it available for six volt system? Thanks!

Jbil,
Fuses & even circuit breakers work on either 6 or 12 volt. Minerva was all stock wiring & 6 volt, with a 30 Amp single wire alternator. On the main supply I used a 30 amp G.M. spade type breaker, mounted with a supplied pigtail lead. Worked very well & simple & cheap. Breaker is a 12 volt, that doesn't matter, as they work by current flow, not by voltage. Smaller amperage breakers can be used on other circuits if desired. The same G.M. breakers are readily available in MANY Amp ratings. P.M. me if I can help. ( If I can't help, maybe the Dog can.) Bill W.

[msmaron]

Originally Posted by captain marty

I am planning on running fuses for each area such as one for low beam headlights, one for bright, one for tail and one for brake lights. My system is original 6V. I've searched for candle power to watts but find there is no conversion. I am running 14 G wiring to all lights.
Thanks,
Marty

Originally Posted by steve s

There is no simple conversion. It depends on the efficiency of the particular light source for converting electricity to light and to a lesser extent on the color of the light. Why not just notice the current draw on the car's ammeter when you turn the load on? Our ammeters are notoriously inaccurate, but they're good enough for this purpose. Just allow a margin and don't go over the ~30 amp rating for non-bundled 14 gauge wire. OR, just follow P.S.'s recommendations.

I would suggest using heavier gauge for the main power line coming out of the alternator or cutout.

I think this is what you were asking about
2w=3cp
6w=6cp
10w=-15cp
16w=21cp
25w=32cp
35w=50cp

so 60w=82cp if i am correct....

Hope this helps...