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I converted over to a 1 wire alternator, I followed the directions from here to a tee. The problem is I have a 100 alt, that is putting out the 100 amps but only about 12.7 volts get to the battery? I checked the alt and it produced 13.7 volts as the rpms increased (I quit going higher so it could produce upwards of more?) anyway only 12.7 gets to the battery and thats at bout 4000rpm. Any thoughts?
Thanks,
Mike
 

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Sounds like you need to up-size the wire going to the battery and or check for bad connections at the horn relay or terminal block behind the battery. There is probably too much resistance and the alternator is holding the system voltage at 13.8 - 14.1 but the extra resitance in the battery circuit is causing the voltage to drop. To verify this in the drive-way, try connecting a jumper cable from the battery + to the alternator output lead and see what you get.

-dnult
 

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As dnult suggests, use a jumper from the BAT terminal on the alt to the battery post. On the newer vehicles with this style of alt, there is an 8 AWG doing the job mentioned. The 1st gen wiring is not set up to do this, you must enhance by adding the wire. Be sure the ground cable is of good repair, #2 or #4 AWG and clean connections all around.
 

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Another interesting and education test would be to measure the voltage between the alternator hot lead and the battery. My guess is that you'll see a couple of volts drop. You can then move one of your meter leads to the various points in the circuit like the terminal block and horn relay. It will isolate the part of the circuit that is causing the drop. But in summary, Everett's suggestion will probably fix it.

On another note though, we didn't really discuss your engine speed. I read somewhere that some 100 amp alternators don't put out below about 1200 RPMs or so. If you rev the motor does the voltage come up? But this is an aside to the need for a beefier circuit.

-dnult
 
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