IH 140 charging system

Before I ask my question let me say I have read through and checked everything on John T's list.

This is a 1972 IH 140, 12 volt, negative ground.

The generator went out while using the tractor a while back, had the generator rebuilt.

When I put the generator back on and cranked it up it was charging fine. I cut the tractor off, just so happened to be standing there while smoke started to come out of the generator, the tractor is off at this point. I managed to get the wires unhooked and the generator still checks out fine.

The lower contacts in the regulator stay in the down position only after the tractor is stated and shut down. The Battery terminal is the only terminal with voltage coming to it but with this contact in this position it is feeding power back to the generator trying to run it as a motor.

I have put a new voltage regulator on on the tractor an the same thing still happens. until I take the power off of the Battery terminal then everything is fine until I crank it back up.

Could something be switched inside the generator causing this problem? Any ideas that does not fall on John T's list?

Thank you for any input.

Best thinking I have:
If a cutout relay will not disengage (open) it is not working correctly. If the Cutout is a 6volt (it could happen!) it might remain closed dispite the reverse current flowing through it.
If it has solid state diodes in the regulator circuit, the regulator must be for the correct polarity of ground. (most IH 12v generator systems were pos ground.)
Those two things could be the cause.
If not the spring that is pulled to make the cutout open (it also resists the closing) could be adjusted for earlier opening and harder closing of the cutout points. Just a little at a time.
With the tractor off, and cover off of the regulator, the cutout movable contact can be pushed closed by hand. If it sticks down, (it has been) the spring is too weak. (use a popsickle stick or plastic knife and open it to avoid smoke. Tighten the spring (it might mean bending a metal tab, or a screw.) (do this with the bat cable removed to avoid more smoke)
Very little adjustment is needed for each attept.
When it finally reopens on its own when released, it is time to try it with the cover on, and the tractor started. (be prepared to remove the cable if when shut off it continues to draw as before)
It might take higher RPM to start charging, that would be a function of that extra spring tension.

If this is still not operational, or you want a simpler answer, put a used diode (pulled from a full sized GM car alternator. Use a diode that stops flow to the gen, but allows it to flow to the cutout. (1/2 the diodes are polarized one way the other half are the other way. If the body of the diode is kept from grounding, either will work. Best of luck, Jim

It was frustration like this that led me to put an alternator on my 1966 140 five years ago. I haven't thought about my charging system since. The replacement regulators you get today are nothing like the original Delcos IH put on these tractors. Bad out of the box is not uncommon. I had gone through a couple of rebuilt/reman generators and regulators in the ten years previous. They just didn't last like the originals did.(about 25 years for both.)

Jim--His tractor, and mine, are definitely 12V negative ground from the factory.

Just trying to cover as many possible faults as I could think of. A modern Positive ground reg might have serious issues with negative ground use. Thanks for the data bit. Jim

I almost put an alternator on it instead of having the generator rebuilt. But it was a little cheaper to have the generator rebuilt.

After buying the third regulator yesterday the alternator would have been cheaper but this one worked. Either it is OK or I did not mess it up. This tractor does not get much use so I have been working on it for a year off and on so I am not able to take the other regulators back, even if I could.

I was reading some older literature that came with a regulator bought 40 years ago or so. It said not to ground the L terminal, I think it was the L terminal, or it would instantly destroy the regulator. So I bought another regulator and made darn sure I installed it correctly.

on this "A" style of regulator/generator, the field terminal on the regulator is grounded internally. As the voltage rises, the ground is interupted using vibrating points. That allows a resistor to be in the ground path when the voltage opens the points, lowering but not eliminating the charge rate.
Hooking voltage to the regulator F terminal from the battery (if hooked to the gen or not) will nearly instantly ruin the regulator voltage control relay/contacts.
Flashing from BAT to F will ruin them.
Yours seemed to have the cutout relay as a problem, I think they were bad from the get go, and you didn't ruin them. Jim