Cub Cadet 125 Voltage Regulator Questions

[Red Dave]

The voltage regulator on my 125 started acting erratically last week when I ran it to plow snow. I gently tapped on it and it gave a nice spark shower, so I figured it was time for a new one. I ordered it from one of the advertisers on this board.

It is listed as the replacement for the original part number, and I have bought parts from this source before with no issues so I am confident it is the correct regulator. But it is different from the old regulator and I am hesitant to wire it up without resolving my concerns.

The old regulator has 4 terminals: GRD, B, G & F. Ground, Battery, Generator and Field. I traced existing wiring and it conforms to both the illustration in the manual (GSS-1398, page 1-29) for Models 72, 104, 124, & 125, in the Technical Library of this site. It also matches the wiring diagram by R. Bedel for those same models. GRD goes to ground, "B" goes to the ammeter, "G" goes to the "A" terminal on the generator and "F" goes to the field. That checks out.

The new regulator has different terminals. It has GEN, F, BAT & L which I interpret as Generator, Battery and Field, which I understand. My question is for the "L" terminal. It has no Ground terminal.

I opened the cover on both and there are internal differences too. The terminals are arranged differently, but as long as I connect it correctly electrically, there should be no issue.

What do I do with the "L" terminal?

I can wire the Field to the "F" terminal, the Ammeter to the "BAT" terminal
the generator armature to the "GEN" terminal, no matter where they physically are, as long as it's electrically correct and skip the separate ground, but I'm not sure what to do with the "L" terminal.

Any help you can offer is greatly appreciated.

[ol'George]

IIRR "L" terminal was for lights on some models.
Your ground terminal should be via a braided wire to a mounting bolt usually near the rubber foot of the regulator.

But wait till others validate this as on some things my memory is not the best.

[Red Dave]

Originally Posted by ol'George

IIRR "L" terminal was for lights on some models.
Your ground terminal should be via a braided wire to a mounting bolt usually near the rubber foot of the regulator.

But wait till others validate this as on some things my memory is not the best.

I thought about "L" for Lights too, but I'm not positive about it.
It has lights and as far as I know they are original, but they are fed from the wiring harness.

Thanks for the thoughts.

[Billy-O]

I think the L is for Load. The earlier Cub Cadets had regulators using B, G, F, L and ground. The 125 uses B, G, F and ground.

[darkminion_17]

L is for load, I believe it is always live even with the key off so put a piece of tape or shrink tubing over it. That regulator is for the Original, 70, 100 starting system and will work fine in your application.

[Red Dave]

Thanks Billy-O and Darkminion.

You've confirmed what I was thinking (and hoping). Didn't want to wire it wrong and let the smoke out of a brand new Regulator.

I appreciate the help.

[Red Dave]

I put the new regulator on. Started it up and it charged about as I would expect it to. Was ready to declare victory, but as I drove it around the yard for about 10 minutes, suddenly the amp gauge went to full discharge. Tapped on the regulator with my hand and it went full charge. Then it started fluctuating up and down wildly. I put a voltmeter on the battery and the voltage was doing the same thing as the ammeter, which makes sense.

So it's back to the drawing board.

Now I need to determine if I got a bad new regulator, or if there is a bad connection some place in the wiring.

It's always something.

[ol'George]

Check all the connections and that you have a good ground @ the regulator.
Also the Bat-tree connections.
When was the last time you looked at the Gen brushes?
Might be a good thing to check after you check the wiring.
Remember grounds are just as important as the + wires.

[Billy-O]

Last summer I had issues with my 125 charging system and determined the problem to be faulty regulator by borrowing a known good one from my other 124 tractor. The swap fixed the problem. I then replaced the faulty with one I bought online. This resulted in my charging meter being erratic jumpy. I then requested replacement for the faulty. The seller sent another one and the results were the same.... Jumpy meter. Eventually, the seller refunded my money and I kept the two faulty new regulators (seller did not want them back). My 125 is still borrowing the regulator from the 124.

I'm not sure exactly what the problem was with the new replacement regulators but I have a pretty good idea they were just crap from overseas. Take a look at the attached photo and compare old on left with junk on right. The wiring layouts between the two are very similar including the hookup tangs for F, B, L, G and ground. The new reg has the G hookup on the bottom but same side as old. Note the the # windings of thick wire on the forefront coil of both regs.. The old one is wrapped 5 more times than the new. Not sure if that makes a difference. Can anybody see the missing pop rivet on the switch lever over the coil of the new reg? That could make poor contact. I'm not sure if you guys can see how poorly the contacts aligns with each other on the new. The contacts on the old aligns together nicely and provides a solid contact.

IMG_20240131_153537359.jpg

[darkminion_17]

You can try to bend them to line up, but be aware of the voltage output at the battery.