Regulator wiring questions...... again

Hello All,
Last week there was a post in the JD forum about wiring a Genny on a JD 'D", one of the replies supplied an excellent link to a Delco voltage regulator manual.
In that manual, it showed the correct way in which a 3, and a 4 terminal voltage regulator are wired.
I have a 1948 John Deere BW, Iv'e owned for about 6 years, in that time, I have had charging issues on two occasions, both times the charging system troubleshooting pointed to the regulator being bad, it had a 4 terminal regulator on it when I got it and the regulators I purchased were also 4 terminal, the first was an inexpensive one, the last was a "premium" USA made version that was kind of pricey.
After installing and polarizing the new regulator this last time, it did not charge, once again I checked all the connections, amp meter shows a discharge when lights are switched on, regulator base is properly grounded, then, when regulator field terminal was grounded, it starts charging, once again pointing to a defective regulator.....so, I call the supplier of the regulator, tell him what I just said, he says it is probably a bad regulator, and happily sends me a new replacement.
So about this time is when I stumbled on the post about the JD D wiring, and the replies from our forum Guru's, and the manual on the Delco regulators, Then I decided to dig in to the wiring on the tractor. Even though there is not much to the wiring on the B tractor, It was put in plastic split loom and overly taped up,it was all contained in the loom, with the exception the terminals connected to the amp meter and the voltage regulator. I took the dash loose, which I had not done before, exposing the gauges and removed the harness and opened it all up.
The light switch was wired off of the amp meter, and there was also a wire coming from the same terminal on the amp meter, going to the load terminal on the regulator, this according to the delco manual is NOT correct for a 4 terminal regulator, which I have been using.
After installing my new replacement 4 terminal regulator and wiring it as per the delco manual, the tractor charges perfectly with or without the lights on,So....
After all this rambling,I have two questions;
1. Did I destroy the "pricey" USA made voltage regulator by installing it on a tractor with incorrect wiring ? I realize now that the "L" terminal on the regulator is the source to supply voltage for lights or ignition. Would running power from the amp meter to the "L" terminal cause damage to the regulator or generator ? If that's the case I need to get in touch with suppler and pay for the replacement he sent me, and if so;
2. Why did the first regulator I installed a few years back, work for a while and then give out instead of just frying like this last one ??
I Appreciate the Knowledge shared in these forums, and any input on this as well. Thanks...Tom
John Deere D

Connecting the leads from the regulator's "BATT" terminal and "L" terminal to a common point (ammeter terminal, in this case)
would "shunt" around the "current winding" in the regulator so there'd be NO current regulation of the generator's output current.

Whether that would damage anything either instantly or over the long term would depend on what current output the generator is capable of and the loads powered and battery condition.

<img src = "http://oi63.tinypic.com/51boea.jpg">

First of all its the Generator NOT the Voltage Regulator that gets Polarized.

1. Did I destroy the "pricey" USA made voltage regulator by installing it on a tractor with incorrect wiring ? I realize now that the "L" terminal on the regulator is the source to supply voltage for lights or ignition. Would running power from the amp meter to the "L" terminal cause damage to the regulator or generator

I cant say how the incorrect wiring was configured so cant answer that question HOWEVER one way to harm a Voltage Regulator is if the genny were incorrectly polarized and you start the tractor.

I doubt running power from the L terminal to the ammeter damaged the Voltage Regulator



2. Why did the first regulator I installed a few years back, work for a while and then give out instead of just frying like this last one ??

If a VR is designed specifically for one ground and you use it at the opposite the contacts can be harmed. The Delco literature Bob posted explains some of that. A VR needs a good ground to work, I just cant say why yours fryed.

John T

The tractor is positive ground, that I am sure of.
I ran a jumper from the base of the regulator, to the grounded side of the battery with no change . I am sure the regulator has a good ground.

Hello John, Happy Easter Everyone,
I changed the diagram in Bobs post to show how the "incorrect" wiring was configured.
I polarized by momentarily touching bat & gen terminals with a jumper.


I cant say how the incorrect wiring was configured so cant answer that question HOWEVER one way to harm a Voltage Regulator is if the genny were incorrectly polarized and you start the tractor.

I guess I'm wondering what the "L" terminal would be used for.

"L" terminal would go to power lights or ignition, instead of connecting these to amp meter.

Ozlander, to answer your question, with the "lights" being fed by the "L" terminal the regulator doesn't "see" the lighting current and continues to charge the battery at the same rate as if the lights were not being used, thought to be better for the battery, I guess.

<img src = "http://oi68.tinypic.com/25i829l.jpg">

You can download the complete Delco document at the link below. (20 pages.)
DR5134