4020 12v Conversion - Gen Light Update

Still having issues getting gen light to work as it should. Tractor was previously wired as pictured with "s" terminal connected to the "B" terminal with the short red jumper wire.....alternator was charging but light not working. Per prior input from this site, we hooked the "G" which we thought wound be the same as the #1 terminal to the gen light. Light did not light with key on despite having power to it.

We then hooked "S" terminal to the key switch and "G" to gen light.....same results. We then switched wires so "s" was go to gen light. Light would then light with key on (progress huh!!), but would not go out when tractor started. In addition, alternator was not charging with this set up. Looking for suggestions on getting to gen light to work and alternator to charge as well. This John Deere reman alternator is different than the previously discussed Declo alternators with numbered terminals. Just trying to get the little dash light to work!!
mvphoto16326.jpg
 
Bottom line is that the Nippondenso alternators require more "excite" current than the 10 or 12 SI Delcos and the current draw of the "idiot lite" is not enough to "Excite" the alternator..

Try this... start the engine (careful to keep body parts out of moving parts), and momentarily jumper the "S" and "IG" terminals.

Light should go out, and alternator should excite and charge.

Once it's charging and the idiot light is out, it should continue to charge until it's shut down, and restarted later.

The "fix" is to put a resistor across the "idiot light" to provide more "excite" current.

Been a long time since I've worked with one of these and can't remember what value I've used, probably have some info in my notes at the shop.

You might try a 10 Ohm 10 Watt ceramic resistor.
 
Thanks I will give that a try. You recommend putting a resistor "across the idiot light". Not sure what you mean....How would I wire the resistor in. Just in the wire coming from the alternator to the idiot light?
 
I have never tried using a Nippo with a light but had
been told that they would not operate a light. I've always
used Delcos on older tractors.
 
no. across means in parallel. what you described places the R in series. connect one end of R to a lead of the idiot light and the other end of the R to the opposite lead of the idiot light. R is the resistor.
 
Sorry, Been here and done that. If you want the generator light to function, get a Delco alternator or a Motorola. The Nippon Denso electronic circuitry will not allow this function. Without any doubt this Series of Nippon Denso alternator was the best ever offered for John Deere products (IMHO) If you want to use it and be able to monitor its output, plan on installing a volt meter for it. Indicator light is not an option with this alternator.DW
 

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