106-check my diagnosis

[jbrewer]

Originally Posted by save_old_iron

John,

sounds like multiple problems on the tractor, especially since there are "a few leads that aren't connected to anything".

What a great post, thank you, and I'll give that a look. I think that's what Vince was referring to also in his post. I do have an extra regulator, but since I like taking stuff apart, I'll do this when I get a spare moment. Again thanks for taking the time to photograph this, it'll be a huge help.

Mechanical regulators are interesting beasts. I'll have to find a schematic that included the details of the coils and contacts inside the "black box" , as it would help explain this sneak path for current. In any event I'd like to understand these things...whether there is electromechanical hysteresis built in and how, etc. They're remarkably reliable for what they are.

Re: the "extra wires"...I suspect some are for lights, etc. There's one violet wire that comes out of the harness at the S/G area that doesn't seem to go anywhere and there's a small red wire...maybe 18G at the dash tower that disappears into the harness that is not connected either, but has a nicely terminated ring terminal on it.

John

[jbrewer]

Originally Posted by Matt G.

That series has wiring harnesses that deteriorate badly after 40 years, so the first thing I would do is re-do the wiring harness. It also sounds like the ignition switch could be bad, which is easy to check with a multimeter.

Hi Matt

Surprisingly enough the wiring looks pretty darned good. There's not been a huge amount of buggery from the PO, other than the cigarette lighter wire he attempted to connect to the ammeter with what looks like #22 wire.

Ohms mean things :-)

John

[Matt G.]

'Looks good' and 'is good' can be two different things. I've had more than one harness develop issues where it goes between the engine and frame. I think the heat from the engine deteriorates the insulation but not the loom, so serious problems can develop out of sight. BTDT.

[save_old_iron]

Originally Posted by jbrewer

Ohms mean things :-)

John

[save_old_iron]

John, checkout the diagram below. This might help to understand the "runaway" SG motor.








I have taken a few "technical liberties" with this explanation in order to foster a deeper understanding - but here goes.

The SG is turning slowly while engine is cranking. SG output is a very low voltage during cranking. This low voltage is sent out the "A" terminal and enters the regulator "G" terminal. For the sake of discussion, let us say the SG voltage output is 5 volts while cranking.

The 5 volt output is sent to the blue windings of the cutout relay. The magnetic field created by the 5 volts applied to the relay is NOT STRONG ENOUGH to pull the relay contacts together. The battery and the SG motor are electrically isolated by the open contacts. The engine fires up - the SG motor speeds up - the voltage out of the SG now rises to above 10 volts and BINGO - the 10 volts from the SG applied to the cutout relay blue windings is now strong enough to pull the relay contacts together. Now the battery and SG are electrically connected together thru the cutout relay.

The SG produces a voltage which is HIGHER than the battery voltage so the SG charges the battery - nice.

When you shut down the engine, the SG also slows down - so voltage from the SG now decreases until the cutout relay no longer can hold the contacts together. Once again the cutout relay contacts open and electrically disconnect the battery from the SG motor - as it should.

But what if the cutout relay contacts become stuck together when the ignition key is turned off?
The battery current can continue BACKWARDS from the battery thru the stuck relay contacts back to the SG and enable the motoring function in the SG.

This condition is overloading the wiring of the SG regulator. The #6 gauge wire that normally passes the starter current to the SG now tries to flow thru the #14 wire attached to the regulator "G" terminal back to the SG's "A" terminal. This wiring cannot support the high cranking current needed by the SG motor. The wiring was only designed to pass 15 amps max from the generator to the battery. Things can overheat quickly.

Hope this makes some sense - I'll be in and out over the next few days if you have any other questions of the SG.

Chuck

[jbrewer]

Chuck, you nailed it. Lew had it right also!

I finally got some time today to pull the V-regulator off. There's only 2 solenoid wound coils, but one of them indeed did have a huge nub on it where the material had transferred from repeated arcing.

I filed it down, reinstalled and off we went. All is working fine now. This is a great pictoral and really should go into the Technical Reference section for the next guy that runs into this problem. Thanks for all the hints and especially to you Chuck for the great photos and graphics and in particular, the explanation. It makes sense and that was EXACTLY what the issue was.


John

[ACecil]

Originally Posted by jbrewer

Chuck, you nailed it.

I finally got some time today to pull the V-regulator off. There's only 2 solenoid wound coils, but one of them indeed did have a huge nub on it where the material had transferred from repeated arcing.

I filed it down, reinstalled and off we went. All is working fine now. This is a great pictoral and really should go into the Technical Reference section for the next guy that runs into this problem. Thanks for all the hints and especially to you Chuck for the great photos and graphics and in particular, the explanation. It makes sense and that was EXACTLY what the issue was.


John

Glad you got it fixed, John!

[Methos]

Originally Posted by ACecil

Glad you got it fixed, John!

Oh yeah!

[jbrewer]

Originally Posted by Methos

Oh yeah!

Lew and Chuck both had it right. That's a really obscure (to me) fault that would have really driven me further up a wall than I normally am.

You know that feeling when you take something apart and the "Ahah " moment occurs .

Now to fix the clutch on this thing, clean it up and use it. It's got a very VERY quiet replacement motor a new steering box and is a nice ride!

This forum is the best
John

[save_old_iron]

John,

You"re welcome. Hopefully those diagrams help. I think most times one picture can be worth a thousand words.

Chuck