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Allis Chalmers Discussion Forum

alternator wiring OOPS?

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10-14-2003 20:19:29

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have thought about makeing an alternator test stand for several years. completed it today. had an old DELCO 10SI alternator that i thought had a bad regulator, but put on the stand just to test the motor-belt setup. of course the alternator did not work. for some unknown reason i decided to switch the spade terminal wires 1 and 2. guess what, with the dropping resistor on #2 instead of #1, it charges! anyone ever heard of that. dont know what is wrong with the regulator, but it charges when connected wrong>---------
--my plan was to make a small test stand to check a delco 10SI, newer Delco 130, and a couple of the smaller Japaneese alternators to see what size droping resistors work good. just trying to learn more about each. thinking about using a small honda alternator on next "B" tractor.anyway, i made an angle iron frome about 16 inches square. set a old 12 volt battery on one side, and mounted a 1/3 HP washing machine motor on the other iwth the alternator above it. have a small dash board with amp meter, volt meter, and a couple resistors on a patch panel. motor turns 1000 RPM and the alternaotr turns 1500 RPM, good low speed test. connected a headlight (80 watts) as a load. amp meter draws 6-7 amps for the light. when i energize the alternator "signal" terminal the amp gauge jumps to +15, then goes stable to +5 amps and 14.5 volts. tried a 10 ohm and a 100 ohm resistor on the signal line and both appear to work similar. i know i am only getting about 12 amps out of the alternator, but that is dependant on the speed (1500 rpm) and the condition of the battery (fully charged). when i get the smaller delco and the honda tested i will give additional results. bought the 3 year old honda alter on e-bay cheaper than a rebuilt delco from NAPA, should be a smaller package as compared to the old 1975 DELCO.

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Rod (NH)

10-15-2003 16:57:08

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 Re: alternator wiring OOPS? in reply to steve, 10-14-2003 20:19:29  
Hi Steve,

Dropping resistor? I have two Delco 10SI coversion installations. One is on my AC-B and the other is on my Oliver 77. I don't have any resistor in the wiring. They have worked fine for months. I have read about the apparent need for either diodes or resistors but am unclear as to what, where and why. For an internally regulated 10SI I just connect the #2 terminal directly to the main output stud and the #1 terminal gets +12v directly from the battery through a switched connection, initiated by either ignition or oil pressure. What am I missing out on by not using some type of resistor (or diode) somewhere?

third party image Rod

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Doug in OR

10-15-2003 18:12:35

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 Re: Re: alternator wiring OOPS? in reply to Rod (NH), 10-15-2003 16:57:08  
You have it wired correctly, Rod. You need a diode in the exciter line (pin 1) if this line goes back to your ignition switch and ignition circuit. Reason being that the voltage will feed back and keep your ignition energized - hence you will not be able to shut the tractor off. Using an indicator light on this circuit will usually drop enough voltage that run-on will not be a problem. Personally, I use a resistor (47 ohm, 5 watt) in series with my diode; merely as protection.

And yes, I don't know why Steve would need any resistor in his alternator configuration. BTW, you can easily use Nippondenso alternators out of an old mid-80's Toyotas too. They are smaller when size is an issue.

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10-15-2003 19:14:05

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 Re: Re: Re: alternator wiring OOPS? in reply to Doug in OR, 10-15-2003 18:12:35  
the resistor serves the smae purpose as an idot light on the dash. i was told years ago by a delco rep the alternator would charge at a lower RPM (kick in) if a resistor was used in the #1 pin. i did more checks tonight. i apparently have a smll problem with the voltage regulator internal. with 12 volt to both pins it will charge o.k. when i take the #1 pin off and put the resistor in line, i have 7 volts at the pin not running, and 17 volts when running, but no output from the alternator. with it connected straight to 12 volts and no resistor, it charges o.k. putting the resistor in the #2 pin was a mistake, but appears to not effect the output. but the way, a .2 amp 12 volt light bulb is equivalent to aabout 50 ohms, 2 watt resistor. i never realized you could just connect the #1 to 12 volts, always thought it had to have a lesser voltage to get it to kick in. live and learn.

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Doug in OR

10-16-2003 06:22:53

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 Re: Re: Re: Re: alternator wiring OOPS? in reply to steve, 10-15-2003 19:14:05  
Pin 2 is your sense line, Steve. You can connect it straight to the BAT terminal on the alternator. A purist would run it to the battery. It doesn't matter - the difference in supplied voltage would be slight. If this pin is not connected to one place or the other, it might explain why you are getting 17 volts.

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Rod (NH)

10-15-2003 19:09:53

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 Re: Re: Re: alternator wiring OOPS? in reply to Doug in OR, 10-15-2003 18:12:35  
Hi Doug,

Thanks a lot for the explanation. It makes sense now and explains why my current wiring works well. My Oliver is a diesel (no ignition switch) and #1 alternator terminal gets +12v through a N.O. oil pressure switch I installed just for that purpose. My B has a magneto ignition, hence no ignition switch in any conventional sense. There I use a DPDT 2 pos toggle switch to 1) ground the mag and stop the tractor in the "off" position and 2) apply +12v to the #1 alternator terminal in the "on" position. So on both tractors there is no mechanism for any feedback into anything, therefore no problems and no need for any resistor or diode.

third party image Rod

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