Losing volts - Chevelle Tech
Electrical & Wiring Troubleshooting electrical problems.

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post #1 of 16 (permalink) Old Jun 2nd, 14, 3:55 PM Thread Starter
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Losing volts

Hi, i have a 125 one wire alternator on my chevelle. I have 1 12" electric fan. I have a relay on hooked up and i am still loosing a volt. It's a 15 amp fan. So i don't understand why I'm losing that. On idle i have 12.5. When fan isn't on i have 14.1. Can anyone help?

Thx

Wes


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post #2 of 16 (permalink) Old Jun 2nd, 14, 4:14 PM
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Re: Losing volts

You have excessive drop due to too small a wire from the alternator to the terminal post behind the battery. Increase the wire size and/or get rid of the one wire alternator.

Make sure the power for your fan is coming from the terminal post.

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post #3 of 16 (permalink) Old Jun 2nd, 14, 4:54 PM
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Re: Losing volts

At which location are you making the measurement? Try measuring voltage at idle with the fan on at these locations: Battery (+) terminal, the output stud on the alternator and at the fan itself. If the alternator is hot putting out 14v at idle, it may be time to change to a different type of alternator that has better low speed output.
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post #4 of 16 (permalink) Old Jun 2nd, 14, 6:47 PM Thread Starter
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Re: Losing volts

I have a 10 gauge wire from alt to starter. I have tried it at the alt, batt and at the gauge in truck and they are all within .3 of a volt of each other.


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post #5 of 16 (permalink) Old Jun 2nd, 14, 6:48 PM Thread Starter
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Re: Losing volts

Quote:
Originally Posted by ISkagZilla View Post
I have a 10 gauge wire from alt to starter. I have tried it at the alt, batt and at the gauge in truck and they are all within .3 of a volt of each other.


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A 10gauge wire to the battery post in the starter


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post #6 of 16 (permalink) Old Jun 2nd, 14, 8:40 PM
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Re: Losing volts

Unless you have rewired the car what you have at the starter does not matter. Power is distributed from the terminal post located behind the battery next to the passenger side headlights.

10AWG is way too small for the starter conductor...you sure that is the size? Pictures?

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post #7 of 16 (permalink) Old Jun 2nd, 14, 8:47 PM
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Re: Losing volts

And in addition, this exactly why 1-wire alternators lack in the area of remote sensing.

Even if the wiring is bumped up, there is going to be voltage drop(s) present, and traditional automotive alternators set-up correctly with remote sensing would compensate for this.

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post #8 of 16 (permalink) Old Jun 2nd, 14, 9:12 PM
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Re: Losing volts

You may have a wire size problem, but more likely the alternator is the culprit. One-wire alternators are notorious for low output at idle. They lack the sense circuitry of conventional GM-engineered units.

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post #9 of 16 (permalink) Old Jun 2nd, 14, 10:47 PM
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Re: Losing volts

There's nothing wrong with a one wire alternator. Doesn't have sense circuitry? There internally regulated which does the same thing as a externally regulated generator. The op didn't mention what happens off idle or if he revs it. Has the alternator been tested or what state the battery is in. This may or may not help you but I ran a 8ga from the alt directly to the bat. I wouldn't expect a whole lot at idle if you take the truck to a shop and they test the output and you watch the alt load test is done at 2000 rpm not idle.

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post #10 of 16 (permalink) Old Jun 3rd, 14, 12:59 PM Thread Starter
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Re: Losing volts

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Originally Posted by zombie1969 View Post
There's nothing wrong with a one wire alternator. Doesn't have sense circuitry? There internally regulated which does the same thing as a externally regulated generator. The op didn't mention what happens off idle or if he revs it. Has the alternator been tested or what state the battery is in. This may or may not help you but I ran a 8ga from the alt directly to the bat. I wouldn't expect a whole lot at idle if you take the truck to a shop and they test the output and you watch the alt load test is done at 2000 rpm not idle.

The alt has been tested and it's fine. The battery is a yellow top brand new. I was gonna use a 4ga and i am hooked to the battery post on the starter. The wire is only 18 ins long.


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post #11 of 16 (permalink) Old Jun 3rd, 14, 4:56 PM
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Re: Losing volts

Without a fusible link from the alternator to battery there could be a fire..

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post #12 of 16 (permalink) Old Jun 3rd, 14, 5:08 PM
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Re: Losing volts

Is there a relay hooked up to the fan ?
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post #13 of 16 (permalink) Old Jun 3rd, 14, 6:09 PM
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Re: Losing volts

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Originally Posted by bikeron View Post
Without a fusible link from the alternator to battery there could be a fire..
Never used a fuse but if I were to I'd use an actual fuse just because it's much easier to replace. Would have to be a good size fuse though and I'd rec having spares. But here's the problem with that. Where do you place the fuse? You have power coming out and you have power at the bat so you would need a fuse at both ends to be truly protected. Why I don't bother don't need the headache.

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post #14 of 16 (permalink) Old Jun 3rd, 14, 7:19 PM
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Re: Losing volts

An "actual fuse" for a main high-current feed is a bad idea. Even modern GM uses "mega fuses" which are almost more mechanical then fuse with tightened down fittings and assemblies.

Most people try to use traditional glass or plastic "snap on" fuses. Bad idea. These suffer from resistance build up on the contacts which eventually leads to catastrophic destruction of the fuse and the holder.

Fusible links are unsurpassed in reliability, that why they have been used by auto makers for so long. Most fried fuse links are due to user error, either in design or maintenance.

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post #15 of 16 (permalink) Old Jun 3rd, 14, 7:45 PM
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Re: Losing volts

Quote:
Originally Posted by Coppertop View Post
Fusible links are unsurpassed in reliability, that why they have been used by auto makers for so long. Most fried fuse links are due to user error, either in design or maintenance.
Yes,,,

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