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Tractor Talk Discussion Forum

Delco Alternator Wiring - Reversed Terminals

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Jim Bloss

12-30-2004 15:17:20




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I just wired up the alternator that came on my 8N. According to all I have read the #1 terminal which is the field terminal should be hooked to the ignition switch and the the #2 terminal which is the sensing terminal can be hooked up to the alternator output terminal. I tried this. There was no alternaot output and the tractor could not be switched off. I switched the wires on the #1 and 2 terminals. (The #2 terminal came with a jumper wire to the output terminal.) It now charges and the ignition switch now turns off the engine. Does anyone know why this appears to be working or am I being fooled?

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buickanddeere

12-31-2004 10:40:25




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 Re: Delco Alternator Wiring - Reversed Terminals in reply to Jim Bloss, 12-30-2004 15:17:20  
Run the #2 back to the pos post of the battery. Charging will be faster/more accurate as VD on the wiring harness will be compensated for. This is even more important on boats, motor homes etc where "long distances" separate the batteries from the alternator.



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Bus Driver

12-31-2004 03:24:06




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 Re: Delco Alternator Wiring - Reversed Terminals in reply to Jim Bloss, 12-30-2004 15:17:20  
To comment additionally about the device in the lead to terminal#1, exciter, to prevent igniion feedback, the choices are a lamp, a resistor, or a diode. On the tractors that IH equpped with Delco 10si alternators, IH used a 25 ohm wirewound resistor. The typical alternator instrument panel warning light has about 55 ohms. I think the resistor is the most rugged of the 3 and the simpler to install- unless one needs the warning light as an indicator. Since the exact value of the resistor is not critical, I use 44 ohm 5 watt wirewound which the local electronic supplier has. Do not fail to attach lead #2 to a point where it can pickup (sense) the voltage of the system. If not attached, the output voltage may become high enough to ruin the diodes in the alternator.

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jdemaris

12-30-2004 19:12:45




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 Re: Delco Alternator Wiring - Reversed Terminals in reply to Jim Bloss, 12-30-2004 15:17:20  
The inability to shut off the engine is a common problem when using this system with a gas engine. Using a diode or a 15 ohm resistor in the #1 line will fix it, or . . . use an automotive type ignition switch that has an ignition terminal and an accessory terminal. Hook the accessory terminal to the #1 post of the alternator but keep the ignition feed hooked to the ignition post. This isolates the two so the alternator cannot backfeed to the ignition. In automotive use, either an indicator lamp or a resistor wire with 15 ohms resistance is used to feed the exciter circuit that goes to #1 on the alternator. #2, as stated earlier, can go directly to the large output post. Again, in automotive use, is usually does not and runs to the battery instead because of minute differences in voltage and voltage sensing. It won't make a difference on your tractor.

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Bob

12-30-2004 16:27:34




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 Re: Delco Alternator Wiring - Reversed Terminals in reply to Jim Bloss, 12-30-2004 15:17:20  
The reason it didn't shut off was that a "idiot lite" or diode is needed in the wire from the ignition switch to the "1" terminal of the alternator to eliminate alternator charge current backfeeding to the ignition system when the key is switched "OFF".

Also, charging current was PROBABLY flowing the same way, and bypassing the ammeter, and that was why you were not getting a "charge" reading.

I you leave it as you have it, it will almost certainly discharge the battery while shut down overnight, or over a day or two.

The #1 terminal is correctly called the "excite" terminal, NOT the "field" terminal.

During the transition from the old externally-regulated alternators to the internally regulated alternators, a number were built with a "dummy" voltage regulator installed that brought the "R" and "F" connections out through a plug which connected them to an external regulator in the same manner as the older series of alternators.

Newer-style alternators so-equipped have the 2 termianls side by side [II], unlike the internally-regulated versions that have the terminals edge-to-edge [--].

The 10SI or 12SI alternators have dual labeling on the terminals (F1 R2), but the "R" an "F" markings are a carryover from those transitional alternators and do not apply to the internally regulated units.

If you want to know what your alternator is REALLY doing, use a QUALITY digital voltmeter or a good analog voltmeter, and check the voltage at the battery. (Some lesser-quality digital meters cannot cope with the electrical noise generated by the ignition and charging systems, and will give "wild" readings, if they work at all.)

After sitting without charging for a while, the battery voltage will read about 12.5 Volts.

After starting, if the alternator is working, the voltage will come up to between 14 and 14.75 Volts, and the regulator will control it there.

Here's a link to a site with GOOD Delco alternator info:

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twopop

12-30-2004 16:10:42




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 Re: Delco Alternator Wiring - Reversed Terminals in reply to Jim Bloss, 12-30-2004 15:17:20  
the # 1 terminal is the relay term.the #2 terminal is the field terminal and should be hooked to the ignition switch.the # 1terminal should be jumpered to the output terminal.without a diode or idiot light in the ignition circuit,the motor would not turn off,since when the alt.is charging the 1 and 2 circuits are connected and power is fed back into the ignition.once the alt.is excited it will continue to charge even with the key off,until the alt.stops turning

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Bob

12-30-2004 16:31:37




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 Re: Delco Alternator Wiring - Reversed Terminals in reply to twopop, 12-30-2004 16:10:42  
TwoP,

Sorry to criticize, but if he has a typical Delco 10SI or 12SI alternator, your post is WRONG!

#1 = Switched "excite"

#2 = Voltage sense

Jumpering #1 to the output terminal WILL lead to a dead battery overnight.

You doubt? Check out the site I previously posted.

Bob.... The alternator repair guy.



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twopop

12-30-2004 19:16:50




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 Re: Delco Alternator Wiring - Reversed Terminals in reply to Bob, 12-30-2004 16:31:37  
well i didnt take the time to read your link,just went out and looked at a wired alt.instead of just an unwired one.when i get an alt.i also get the two wire connector from napa.just went to check my tractor.YOUR RIGHT.the large wire is the jumper and goes to 2 the small excite wire goes to 1.
crs, you know



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Bob

12-30-2004 19:27:15




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 Re: Delco Alternator Wiring - Reversed Terminals in reply to twopop, 12-30-2004 19:16:50  
I wasn't nitpicking, but errors on these help boards kinda scare me. Someone is looking for help, and gets the wrong info, which could make the problem worse!

And I'm not pointing fingers I have made glaring boo-boos myself, and come back to retract and correct what I said. A person just hopes anyone reading the thread reads all the posts, including any corrections before acting!



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