I'm really close to finishing the wiring on my v8 engine and 12v conversion on my 1950 F1. I'm wiring the alternator similar to the factory wiring, where it connects to the factory circuit breakers on the back of the gauge cluster. My alternator is the typical one wire unit with the amps I don't remember but probably 80? The amp gauge works with the needle way over to the right. Can the factory breakers handle the alternator or what do you do? Thanks in advance, Kurt

 

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I suspect you have the ammeter wired wrong. The battery wire should be going thru the loop, not the wire from the alternator. If the battery is real low, then it would peg over to the right.

I'm using a 65-amp alt with the stock breakers, supplemented by two additional breakers and 5 fuses. The stock CB's will work fine as long as you only connect more or less the same stuff to them as stock. Each of them will be drawing 1/2 as much as they did on 6v,, so the wiring needs to be beefy or the CB's won't trip before the wires smoke off, in the event of a short.

 

Thanks very much for the info. I wasn't clear, yes the battery wire is going through the charging gauge. It's looped twice through, which I think is the correct way? I've been cranking on this new battery a lot for the last couple months, and it's probably a little low. I haven't got the truck running long enough to charge it up. I should put the charger on it then start it again and see how far tot he right it is. Thanks again, Kurt

 

It doesn't need to be looped, I'm surprised that lets it work.

I wasn't totally clear on the CB's either. CB's and fuses are to protect the wiring, not the loads. If you have a 30 amp CB with an 18 gauge wire going to a load, and the load or wire shorts, the wire will be glowing red hot all along its length, burning off insulation and possibly starting a fire, before the breaker trips. The stock wires (6v) are all pretty beefy. If you have rewired with 12v-appropriate wire gauges, you may want to replace the two big CB's (30 and 15 amps) with multiple smaller ones or fuses. They are still used in various ratings on many kinds of vehicles (Harleys for one).

 

F-6 Electrical X

Looping the alternator output wire through the ammeter will effectively show twice the amperage. This is a Hall Effect meter so it's pretty sensitive, but accurate. Also, you have to be sure it's feeding in the right direction. Alternator→circuit breakers→ammeter. Follow the red wire. Disregard the cutout relay, that's my idea for preventing backfeed.

 

I should add that your alternator wire should be AWG 8 if your alternator output is rated over 80 amps. This will also compensate for any voltage drop. Also, you will need a smaller pulley so your alternator will spin up to achieve the rated output. Maybe you have already considered this.

 

Once again, thank you all for the info! I don't know where I thought this should be looped twice through the charging gauge, but that's probably why it shows such a strong charges nearly pegging the needle to the right. I'll change that and see what happens. I have #10 wire for the alternator. I kind of wanted an 8 but couldn't find any autoparts or box stores that had 8 stranded wire.Thanks,
Kurt

 

Be aware that AWG 10 only has an ampacity of 30 amps @ 167°F. AWG 8 has an ampacity of 50 amps, which would be your minimum size to use. You may want to consider a 30 amp fusible link to protect the wiring if you use the AWG 10 wire.

 

A 30-amp fusible link would likely blow the first time he started the truck. The surge output to recharge the battery could be greater than that.

I agree the 10ga wire is not up to the alternator's capability, but the ampacity you're quoting is for continuous loads, which this is not. For the length of this circuit, even with deducts for part of the circuit being bundled and in the engine compartment, #8 would be OK, but BOTH the alt output wire to the CB's AND the BAT wire from the CB to the battery need to be that gauge. The largest load is almost certainly the battery during heavy recharging. #6 wouldn't hurt but damn, it would be tough to route under the dash. How on earth did you route #4's??

Some protection is a very good idea, but rated more like 100 amps, one located near the alt and one located near the battery source. Links are for "last chance" protection.

 

Yeah, AWG 4 is the largest wire that will fit through the ammeter induction loop. Wish I knew what his alternator is actually rated for. My bad on the fusible link. He wouldn't really need it if the wires were sized correctly.

 

I went to one box store "Lowes" and they actually had #8 wire where the 3 autoparts stores did not. I stripped out the #10 and am half finished with the 8. Using the 8, I installed a 40A additional circuit breaker, but perhaps I should go with a 50 amp based upon your discussion. I'm trying to find some info on my alternator. Thanks for your input and helping me out. Kurt

 

it's a 100 amp alternator.
Natural Finish Ford 1 One Wire 100 Amp Alternator Tuff Stuff 7068 | eBay


Maybe I should get rid of this 100 amp alternator, I see powermaster does sell 60 amp but they are pricey at $160. It's amazing lot's of these one wires are 120 and go to 240 amps. Or can I feel safe with the 100 amp alternator?

 

What are your loads? An alternator won't put out more than is needed to recharge the battery and run loads. Mine is rated 65 amps but I doubt it is putting out more than 15 most of the time.

 

The stranded wire that you get at box stores is most likely THHN/THWN industrial grade. It's not automotive wire. Not very vibration resistant. Your 100 amp alternator is way overkill. A 50 - 60 amp alternator would be more than adequate. Remember that these trucks originally had only a 37 amp generator, so that would roughly equate to a 18-1/2 amp 12 volt alternator. My application has high amperage loads and I'm only running a 80 amp alternator.