Alternator to Starter Black Wire?

Fiat88 · Post by **Fiat88** » Mon Apr 18, 2011 6:42 pm

The black wire which goes to the alternator and then starter is wired like this. Black wire butt conected to 2 red wires. One red wire going to the alternator and the other one to the starter. I was wondering how the factory had it wired? Is the way it is now basically the same concept, I haven't had any problems. Just want to make sure.

The way it is now:

Fiat88 · Post by **Fiat88** » Mon Apr 18, 2011 9:31 pm

Ok I think I figured out how the original wiring was. Is this right?

Black wire to alternator + stud with ring terminal and then crimped to that same ring terminal another black wire which connects to the starter + post. Sound about right?

spider2081 · Post by **spider2081** » Mon Apr 18, 2011 10:45 pm

I believe the larger of the black wires 6m or 8 AWG connects the alternator output B+ or Bat terminal to the same terminal on the starter solenoid as the green battery lead connects. The alternator B+ terminal has 12volts on it as long as the battery is connected in the car. This wire diameter is large because a low battery will take all 65 amps the alternator is capable of putting out.
The smaller black wire 4m or #10 AWG connects the same alternator output B+ terminal to the feed side of fuses 9 and 10 and then on to the ignition switch, cigar lighter and parking light switch.

Hope this helps

Fiat88 · Post by **Fiat88** » Mon Apr 18, 2011 11:05 pm

spider2081 wrote:I believe the larger of the black wires 6m or 8 AWG connects the alternator output B+ or Bat terminal to the same terminal on the starter solenoid as the green battery lead connects. The alternator B+ terminal has 12volts on it as long as the battery is connected in the car. This wire diameter is large because a low battery will take all 65 amps the alternator is capable of putting out.
The smaller black wire 4m or #10 AWG connects the same alternator output B+ terminal to the feed side of fuses 9 and 10 and then on to the ignition switch, cigar lighter and parking light switch.

Hope this helps

Thanks.The only reason I'm concerned is that the 2 red wires butt spliced to the black wire are around 12 guage each(kind of small). I'm going to upgrade them each to 10 guage and solder the connections.

spider2081 · Post by **spider2081** » Tue Apr 19, 2011 7:53 pm

Is there a large wire like #6 or #8 connecting the alternator output to the starter solenoid terminal with the battery lead on it?? I think that is very important.
The red wires are probably something a previous owner did.

Fiat88 · Post by **Fiat88** » Tue Apr 19, 2011 8:20 pm

spider2081 wrote:Is there a large wire like #6 or #8 connecting the alternator output to the starter solenoid terminal with the battery lead on it?? I think that is very important.
The red wires are probably something a previous owner did.

The only wires connected to the alternator output is that one red wire coming off the black wire. This is why I'm not sure if everything is ok.

Fiat88 · Post by **Fiat88** » Tue Apr 19, 2011 8:34 pm

The wires I have connected to the starter post are:
A brown wire, a red wire, battery cable and then another red wire with quick disconnect. I;m confused now.

Fiat88 · Post by **Fiat88** » Thu Apr 21, 2011 1:03 am

I looked at the wiring diagram and it shows that 10 gauge black wire goes from fuse 10 or L then goes to the alternator post and then splits to the starter post. So, in turn the alternator output is sending juice to the fuse box and juice to the starter post to charge the battery. Is that, right? Thanks for any confirmation.

spider2081 · Post by **spider2081** » Fri Apr 22, 2011 9:03 am

My diagram for a 1980 shows a #8 wire connecting the alternator output to the starter post that the battery lead is connected to. I think a #10 is too small to carry the 55 amps the alternator is capable of putting out to charge a weak battery. The other #10 wire connecting the fuses and lights is the correct size.
I think I remember you replaced your battery cable to help with low voltage issues. The wire that connects the alternator to the battery cable is now the weakest link in the circuit. I would make sure it is at least a #8 wire. I installed a #6 on my 1981 Spider. The #8 was melted when I bought the car. The alternator diode was shorted and melted the insulation on the #8 wire when the battery discharged through the wire.

Fiat88 · Post by **Fiat88** » Fri Apr 22, 2011 4:15 pm

spider2081 wrote:My diagram for a 1980 shows a #8 wire connecting the alternator output to the starter post that the battery lead is connected to. I think a #10 is too small to carry the 55 amps the alternator is capable of putting out to charge a weak battery. The other #10 wire connecting the fuses and lights is the correct size.
I think I remember you replaced your battery cable to help with low voltage issues. The wire that connects the alternator to the battery cable is now the weakest link in the circuit. I would make sure it is at least a #8 wire. I installed a #6 on my 1981 Spider. The #8 was melted when I bought the car. The alternator diode was shorted and melted the insulation on the #8 wire when the battery discharged through the wire.

Yes I did put in new 1 gauge battery cable, more for performance and awhile ago i did the "brown wire fix". I used painless wiring brand 10 gauge for the alternator to starter wire. The PO had used 12 gauge wires to link the black wire to the alternator and starter.

Fiat88 · Post by **Fiat88** » Fri Apr 22, 2011 4:40 pm

http://www.powerstream.com/Wire_Size.htm
Looks like 10 gauge can carry 55 amps according to this chart.

Alternator to Starter Black Wire?

Alternator to Starter Black Wire?

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