Weird Starter Gen Issues

[Mike'sHorseBarn 3,351]

My 867 had a snafu at the last show of the season and I just got around to trying to fix it last night. At the show when I shut it off the starter genny would just keep on running until i took the positive battery cable off. I figured the switch went bad, no big deal. So last night i out on a brand new switch and had the exact same problem. That had me scratching my head. I unhooked the generator light and the problem went away. That's weird because the genny light goes from the I post to the B post on the switch and should not cause it to keep the starter generator running. After I did that though I couldn't get the problem to occur again and I ran it and shut it off quite a few times. Anyone have any thoughts on what the heck happened?? 

[Pullstart 68,179]

@WHX??

[Handy Don 14,644]

@Achto, please check me on this, but I seem to recall that...

 

One of the relays in the regulator effectively switches the S/G between S and G. Normally, it switches over when the generator coils of the S/G are putting out a threshold voltage sufficient to charge the battery--around 13 volts. The spring on that relay pulls it to S when there is low or no power from the generator. If it gets stuck in G it could keep the S/G spinning after the ignition is off.

[Mike'sHorseBarn 3,351]

8 minutes ago, Handy Don said:

@Achto, please check me on this, but I seem to recall that...

 

One of the relays in the regulator effectively switches the S/G between S and G. Normally, it switches over when the generator coils of the S/G are putting out a threshold voltage sufficient to charge the battery--around 13 volts. The spring on that relay pulls it to S when there is low or no power from the generator. If it gets stuck in G it could keep the S/G spinning after the ignition is off.

 

I was wondering about that. I was hoping that wasn't that case because it's a brand new Made in USA Regulator 

[Handy Don 14,644]

4 minutes ago, Mike'sHorseBarn said:

 

I was wondering about that. I was hoping that wasn't that case because it's a brand new Made in USA Regulator 

IF I’m right, and IF the regulator has adjusting screws for the two relays, it might be that the spring needs adjusting.

If there are no adjusting screws, it is possible to do it by tiny bends to the spring bracket but I’ve never succeeded with that. I have a now-shelved regulator I could not get to voltage regulate properly (the other relay!) and finally replaced it with an adjustable regulator I picked up at the show. 

[squonk 44,615]

Yes regulator is the cause, The only way the gen spins on it's own is to power up the Armature, and since the key is off the only way for this to happen is a back feed from the regulator. The regulator is connected to the battery on the center terminal.

 

 

 

[Mike'sHorseBarn 3,351]

2 minutes ago, squonk said:

Yes regulator is the cause, 

 

NUTS!!

[Handy Don 14,644]

If you have an ammeter on your tractor, it should show the back flow via the black, red, and green connections in @squonk’s posted diagram that is keeping the S/G spinning. 

[Achto 29,806]

Function breakdown 

• Cutout Relay: This is a one-way switch that closes when the generator is producing more voltage than the battery. This allows the battery to charge. If generator voltage drops below the battery's voltage, the relay automatically opens to prevent the battery from discharging back through the generator.
• Voltage Regulator: This is an electromagnetic switch that turns on and off at a high rate (50-200 times per second).
  • When voltage is high: The regulator's magnetic field pulls its contacts apart, inserting resistance into the generator's field coil.
  • When voltage is low: The magnetic field weakens, allowing a spring to pull the contacts back together, removing the resistance and allowing the voltage to rise again.
  • This cycle constantly adjusts the field current to maintain a steady voltage, typically around
    

    13.5−14.2513.5 minus 14.25

    13.5−14.25
    volts, regardless of engine speed.
• Current Limiter: This function operates when the electrical system's load is high and the battery is low. The current regulator engages to limit the current flowing through the generator's field, which protects the generator from being overloaded. 

 

My guess is that your Cutout Relay is stuck / burned together.

Edited yesterday at 04:44 PM by Achto

[Handy Don 14,644]

20 minutes ago, Achto said:

Current Limiter: This function operates when the electrical system's load is high and the battery is low. The current regulator engages to limit the current flowing through the generator's field, which protects the generator from being overloaded. 

The limiter also functions, as I understand it, to prevent “cooking” a battery while the generator output is strong and the battery is already fully charged. The example I recall is a farm tractor running non-stop for many hours after startup. 

Note that the WH regulators I’ve seen do NOT have the current limiting relay. 

[Achto 29,806]

16 minutes ago, Handy Don said:

Note that the WH regulators I’ve seen do NOT have the current limiting relay.

 

If remember right. My regulators have the 3 coil set up inside, this would include the current limiter coil. If a regulator does not have a current limiter there will only be 2 coils.

 

Edited yesterday at 05:21 PM by Achto

[ri702bill 10,036]

This should be of help... old document, corny illustrations, excellent info.

Delco Remy Regulator Manual 1R-116.pdf

[953 nut 62,155]

            The "GEN" wire from the bottom of your regulator is connected to the "A" (Armature) terminal of your S/G and the cutout relay controls that, soooooooooo bad regulator.            

 

I bet that little wire was getting real hot.

Edited yesterday at 06:43 PM by 953 nut

[Mike'sHorseBarn 3,351]

See I took the cover off the regulator last night and both contacts looked ok. They weren't burned or anything. I took a business card and went through them like a set of points that need cleaned. Like I said, after I did all that messing around everything worked ok which I think it's weird. I don't really want to buy a $100 regulator again lol

[953 nut 62,155]

I guess if you maintain an awareness of the potential for a repeat  performance and can get the battery cable off quickly it is worth giving it another try.

[Mike'sHorseBarn 3,351]

2 hours ago, 953 nut said:

I guess if you maintain an awareness of the potential for a repeat  performance and can get the battery cable off quickly it is worth giving it another try.

 

Battery cable is easily removed rather quickly.

[953 nut 62,155]

         Might want to add a 30 Amp fuse between the battery and the regulator BAT terminal.

[702854boy 248]

I had this problem on my 854 a few weeks ago and it turned out that the electromagnet for the starter part, the gap was too close so the magnet was sticking so it might be worth it to try to adjust the left coil gap if possible.

[Mike'sHorseBarn 3,351]

6 hours ago, 702854boy said:

 left coil gap if possible.

 

Left side if you're sitting on the tractor?

[Handy Don 14,644]

29 minutes ago, Mike'sHorseBarn said:

 

Left side if you're sitting on the tractor?

Firstly, the new regulator may well have had a residue on the contacts that caused the initial problem. I’m betting you didn’t think you’d need to clean them when you did the install. If that is the case, you’ve now cleaned them and you won’t see the issue again!

 

So, to testing:

1. Tractor in neutral, wheels chocked, and regulator cover off.

2.. BRIEFLY tap the left coil’s contact arm to close it. Left is with the external connectors toward you. You should have the S/G start to spin. This is the relay that was sticking and that we’re gonna test.

3. Step back and connect your voltmeter to the BAT connector on the regulator (usually the middle of the three, but double check) and to ground. You should see the battery’s voltage, 12.5 or so. 

4. Start the engine and let it run at high idle for a minute or so. The voltage on the VOM should go up into the 14+ range and not more than 15-ish. 

5. idle the engine. Voltage should drop to the battery voltage after a few seconds. 

6. Ok now we want to see the left relay do its thing switching from “S” to “G” when the S/G gets going fast enough.  Slowly raise the engine above idle while watching the left relay. The relay should change--it should close by itself the way it did with your finger tap. If you have a helper, have them read the voltage while you watch the relay. Call out when the relay closes--the voltage should be 13.5-ish. Slow the engine and see that the relay re-opens as the voltage drops through 13 volts. 

7. The relay’s spring hold the contacts open. If the relay doesn’t close until 14 or more volts, the spring needs to be loosened. If it closes below 13.5, the spring needs to be tightened.

8.  Of course, you can skip steps 1-7 and just run ‘er!

Edited 2 hours ago by Handy Don

[702854boy 248]

1 hour ago, Mike'sHorseBarn said:

 

Left side if you're sitting on the tractor?

Yes and @Handy Don did a good job of explaining

[Handy Don 14,644]

On 11/6/2025 at 12:17 PM, Achto said:

If remember right. My regulators have the 3 coil set up inside, this would include the current limiter coil. If a regulator does not have a current limiter there will only be 2 coils.

 

Perhaps you’ve got replacements? I'd be very interested to see which tractors/engines had the larger regulators new or added.