Re: 3-wire delco alternator

Posted by John T on September 22, 2006 at 07:05:30 from (66.244.90.5):

In Reply to: 3-wire delco alternator posted by novice electrician on September 21, 2006 at 20:37:42:

Novice, Actually, based on some GM data Ive seen and discussions with a GM engineer, I prefer NOT to use a diode (only) but instead a current limiting protection resistor in the excitation circuit and then ONLY if she still runs on when shut down (alternator backfeeds coil) would you need to add the diode. Sure, it will work n charge fine either way (diode or resistor or both or an idiot light in the circuit) but Im an old conservative fuddy duddy who believes an ounce of prevention is worth more then a pound of cure n better be safe then sorry lol

NOTE HOWEVER Ive seen n used em ALLLLL ways (diode or resistor or both or idiot light) n never seen one go bad, but a current limiting protective resistor sure couldnt hurt nuttin n she still works fine that way so "Thats my story n Ima stickin to it" lol Ive NEVER had a problem of trickle discharge on those GM 10 SI's which in theory a diode could prevent. Also, the idiot light systems (light versus diode or resistor) sure have some current limiting protection in the bulbs resistance (which my guess is wayyyyyy more then the mere 10 ohms I use) and they still work fine !!!!!!!!!!!

Although its not required to be so high power rated, I use a 10 ohm 5 watt or so resistor (in lieu of diode) just cuz it may have bigger easier to wire leads and similar, although its not required to be so high current rated, I use (ONLY if needed to prevent backfeed) something like a 5 amp 50 PIV Diode.

Bob n Bob M have those excellent pics n diagrams below, but all I have is my description of how I wire them. Again, either way works fine so its your tractor n you pay your money n make your choices as they say.

Heres how I wire a GM 10SI Alternator and remember, it requires NEGATIVE GROUND !!!!!!!

The big rear main alternator output terminal goes to the wire that used to be connected to the BAT terminal on the Voltage Regulator or Cutout Relay. HOWEVER if that wire wasnt already upgraded, when I convert from a Genny to an Alternator, I replace that wire with a 10 Gauge and it runs from the alternators main output up to the LOAD (NOT to battery/starter) side of the ammeter. I also replace/use 10 Gauge from the ammeters other SUPPLY terminal to the battery/starter.

The little side number 2F Voltage Sense Terminal gets connected (use a short 14 jumper wire) right up to to and with the big main output terminal mentioned above.

For the little 1R side Excitation Terminal, run a 16 or so gauge wire from the ignition switches IGN (which is HOT ONLY when ignition is turned on) terminal and in series with it place a 10 ohm 5 watt current limiting protection resistor (dont really need that much wattage power rating, but they are heavy duty built and easy to wire). Then in the rare event the tractor continues to run cuz of alternator backfeed when the ignition is switched OFF, I add in series a 5 amp 50 PIV minimum Diode. The diode must be wired with negative cathode end to the alternator and positive anode end to the switch. Again, the ratings are not that exact but about any diode over a few amps and 50 volts or so works.

Dont forget to change the battery to negative ground and the coil needs to be wired so the negative goes to ground via the distributor points and the positive gets power from the ignition switch and you have to reverse ammeter leads also if your just now changing polarities.

Good luck Ol John T in Indiana

Replies:

Add a Reply Name: E-Mail: Subject: Comments: Optional Link URL: Link Title: Optional Image URL: Email Notification: If you check this box, email will be sent to you whenever someone replies to this message. Your email address must be entered above to receive notification. This notification will be cancelled automatically after 2 weeks.

TRACTOR PARTS	TRACTOR MANUALS

We sell tractor parts!  We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today. [ About Us ]