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Ripley, Ontario Canada | I am rewiring a gm alternator, and I am not sure how to wire it. I know the big terminal goes to the battery, but the 2 little ones, one wants full power when ever the key is on, and one wants some power at startup, protected by a small risister, but which terminal is which.
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Texas/New Mexico Stateline | I am thinking that #2 goes to your key switch, and the other #1 goes to your amp gauge, light, or resistor however it is set up. This diagram may help:
http://www.geocities.com/jeep_images/electrical/delco_wiring_both.j...
Edited by milofarmer1 4/12/2009 10:14
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Hagen Brothers farms,Goodrich ND | The #1 regulator terminal is the "excite" terminal that starts the alternator charging. It must connect to power only when the ignition is on
or it will run down the battery when parked. It also needs a resistor inline in the #1 wire to limit current flow in and out of the regulator.
I prefer to use a small two wire indicator light like a 70's Ford side marker light assy. The light supply's the necessary resistance and can serve as a charge indicator if the machine does not have a voltmeter or ammeter.
The #2 regulator terminal is the "sense" terminal, which allows the regulator to sense system voltage so the alternator can maintain normal system voltage. The most common place to connect the #2 sense wire is to the big BAT stud on the alternator rear.
Make sure you use a replacement alternator plug from the auto parts store. Do not use un insulated crimp on terminals on the regulator terminals, as the #2 sense terminal is less than 1/8 inch from the alternator case. This wire is hot all the time, un fused and likely will cause an electrical fire if it shorts to the case. The replacement plug is safe, fits nice, looks nice and cost only about $2.
Edited by Jon Hagen 4/12/2009 13:10
 (Delco alternator wiring and 12V conversion.jpg)
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 Delco alternator wiring and 12V conversion.jpg (28KB - 8547 downloads)
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Ripley, Ontario Canada | Thanks that is the picture I was looking for. I had mine wired a little different in that I had # 1 on the start part of the switch and # 2 on the ignition side. But the same idea. |
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SW Ohio | Jon, I agree with you on most points, but if you moved the "sense" terminal out to a buss bar or other 12 volt point away from the alternator wouldn't that use more of a real world voltage for regulation? Also on many systems like this I think the coil is fed full 12 volts ( bypasses the resister ) for starting.
Although the light is a standard way to excite the alternator, it can fool you if the light burns out. No excitation no charge! Found out the hard way on a Jeep many years ago.
Dave |
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Hagen Brothers farms,Goodrich ND | L8Bloomer - 4/13/2009 19:05
Jon, I agree with you on most points, but if you moved the "sense" terminal out to a buss bar or other 12 volt point away from the alternator wouldn't that use more of a real world voltage for regulation? Also on many systems like this I think the coil is fed full 12 volts ( bypasses the resister ) for starting.
Although the light is a standard way to excite the alternator, it can fool you if the light burns out. No excitation no charge! Found out the hard way on a Jeep many years ago.
Dave
Yes on the sense wire. Most factory GM wiring harness have the sense wire connected at least 3-4 ft from the alternator to compensate for some voltage drop in the alternator output wire.
You rarely see more than 1/2 volt drop through the system unless electrical loads are very heavy, most Ag applications do fine with the voltage sense right at the alternator, as long as the alternator output wire is 10-12 GA and in good condition.
In the case of my 64 model 4020 gas engine , I ran the sense wire all the way back to the starter to sense voltage as close to the battery as possible to get the full 14.6 volt output to charge the battery as high as possible. That model has a weak starter and needs all possible ZAP from the battery.
Not sure if I really improved it any, but that seemed like a good idea on the day I did it.
As to the resistor in the #1 excite wire, there are several ways to get er done, using a diode, an indicator light or a fixed resistor.
I still prefer the indicator light for these reasons,
1 The indicator light gives an instant visual indication every time you turn on the ignition, that the resistor(bulb) and all other exciter wiring is working .
2 A replacement bulb is available at most auto, farm and hardware stores for penny's
3 It serves as a visual charge/ no charge indicator.
Sounds like you missed the burned out indicator light for the same reason I catch myself doing. That is I instantly turn the ignition switch from off to crank without allowing a moment to check the warning lights.
I try to train myself, but find myself back to the old instant switch habit time after time. :-)
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SW Ohio |
L8Bloomer - 4/13/2009 19:05
Sounds like you missed the burned out indicator light for the same reason I catch myself doing. That is I instantly turn the ignition switch from off to crank without allowing a moment to check the warning lights.
I try to train myself, but find myself back to the old instant switch habit time after time. :-)
Yes, I like the light very much myself. I just wanted to add the caution to check it as you stated.
I'm afraid I don't communicate as clearly as you do Jon. My reference to the resister is to the one in the coil circuit. It wasn't part of the question, but if someone saved the whole wiring diagram for future projects they may want full voltage to the coil for starting. That may depend on the coil etc. used but some situations call for it.
Thanks for the clarification,
Dave |
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Hagen Brothers farms,Goodrich ND | L8Bloomer - 4/13/2009 22:09
L8Bloomer - 4/13/2009 19:05
Sounds like you missed the burned out indicator light for the same reason I catch myself doing. That is I instantly turn the ignition switch from off to crank without allowing a moment to check the warning lights.
I try to train myself, but find myself back to the old instant switch habit time after time. :-)
Yes, I like the light very much myself. I just wanted to add the caution to check it as you stated.
I'm afraid I don't communicate as clearly as you do Jon. My reference to the resister is to the one in the coil circuit. It wasn't part of the question, but if someone saved the whole wiring diagram for future projects they may want full voltage to the coil for starting. That may depend on the coil etc. used but some situations call for it.
Thanks for the clarification,
Dave
Good tip on the ignition resistor. Most factory 12 V automotive and some tractor systems are wired to bypass the ignition resistor while cranking.
This ability to feed 12 V to what is basically a 6 V coil for hotter spark while starting, has great value for cold damp conditions.
The wiring conversion diagram for an M that I posted, does not take advantage of that available feature. |
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Wiring a GM 3 wire alternator
