Wiring problem

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Wiring problem

Postby feg7846 » Thu Dec 03, 2020 9:09 pm

:worthy: Recently rewired a 1947 cub and converted it to a 12 volt alternator system. Also removed the broken ammeter and installed a voltmeter. It had been sitting out in the weather for about 7 years. Got her running good and thought everything was ok. I had it running on a Jump box and not a battery. When I remove the clamps from either the positive or negative cable on the jump box, it immediately kills the engine. Plain to see that it was only running on battery power. In addition to the voltmeter, I added an on/off switch, added 4 post solenoid (replaced pull type starter), added starter button, and 12 volt coil with internal resistor. Alternator is a Delco with one post and 2 recessed connections. Sure thought I had everything hooked up right and was proud of myself until i removed either the positive or negative cable on the jump box.

Without knowing how it is wired, can any wiring/ignition cub expert out there lead me in the direction of what might be wrong. I can add how it is wired in a few days and that is probably what is needed most for anyone to answer my question. Just wondering if there is something very obvious that i am missing. Thanks for all of my farmall friends. This site is terrific....

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Re: Wiring problem

Postby tst » Thu Dec 03, 2020 9:16 pm

make sure you have battery power at the stud on the alternator to start with, full charged battery should be around 13.5 volts, you cannot test a system correctly with a dead battery

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Re: Wiring problem

Postby Dale Finch » Thu Dec 03, 2020 9:20 pm

This is MY understanding of this topic...could be wrong... I often am! :lol:

If you have battery ignition (rather than magneto), they ALL stop if you disconnect the battery! The battery provides power to the coil, and the charging system "refills" (charges) the battery.

With a magneto, it will keep running, since the magneto provides its own power to the coil.
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Re: Wiring problem

Postby tst » Thu Dec 03, 2020 9:37 pm

an alternator needs a constant power source to charge, NEVER disconnect the battery from it while running, it will damage the alternator

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Re: Wiring problem

Postby Jim Becker » Thu Dec 03, 2020 9:40 pm

Dale Finch wrote:...could be wrong...

You got that right.

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Re: Wiring problem

Postby Eugene » Thu Dec 03, 2020 10:20 pm

1) How did you wire up the alternator? Is it a single wire or 3 wire alternator?
2) How did you wire up the volt meter?
I have an excuse. CRS.

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Re: Wiring problem

Postby inairam » Fri Dec 04, 2020 7:39 am

IMO It is a really good idea to make one change at a time especially with electrical.

If sounds like you are running off the battery and the alternator is not charging and you have a dead battery. I would start by putting the battery on an overnight charge.

I would also pick up this kind of meter. $30-50 on amazon. It tests the battery, and the charging system and is very easy to understand. I keep this just inside my barn I am always grabbing it to test a battery or charging system
charger tester.jpg
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Re: Wiring problem

Postby Gary Dotson » Fri Dec 04, 2020 8:24 am

How have wired the volt meter? If you simply placed a volt meter, in place of an ammeter, that would likely be your problem. Where an ammeter is a, flow through, measuring instrument, a volt meter is not. Your volt meter should be wired: Switched voltage source to positive terminal, chassis ground to negative terminal.
You didn't mention whether the alternator is a single wire or if you have it wired as a three wire. If a single wire, some of them have to be spun up pretty fast to excite.
Make us a diagram, so we can see exactly what you have.

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