1966 JD 110 Electrical Help Please

[Wombat125]

My little old tractor seems to have goofy electrical problem.

The generator light on the dash is supposed to come on at very low engine RPM and also when the generator is not charging properly.

On my tractor the generator light only comes on at very high RPM and then stays on continuously, regardless of RPM until I shut the engine off. It has behaved like this for the one year that I have owned the tractor.

Any ideas what's going on? I have attached a picture of the tractor and also the schematic. Thank you!

 

[atschirner]

I can't tell from your schematic where the second wire from the indicator light goes.

From "normal" automotive wiring the indicator light is between the stator output of the generator and the +12V supply. If the generator is not outputing, current flows through the indicator from the battery, generator windings and finally to ground. With proper generator output there is no to a small difference in voltage so no current flows through the indicator lamp and it stays dark.

Sounds like this is the inverse. It is only lighting when the generator is at full output. Could be that the non-stator wire is grounded.

Trace the wires from the indicator. One goes to the stator of the generator and the other should connect to a switched +12 source most likely at the ignition switch.

Please let us know how this works out for you.

 

[Wombat125]

Wow. That sounds like some good leads to check into [pun intended].

I'll definitely report back, but it might take a while. Considering the age and simplicity of the tractor, the wiring is amazingly difficult to get to. It's in front of the dash, under the gas tank, behind the motor.

Thank you very much for the suggestions.

 

[mfreund]

Could the generator be over charging causing the light to come on?? Bad regulator?? Put a voltmeter on the battery to see what it is charging to.

 

[irwin]

Could the generator be over charging causing the light to come on?? Bad regulator?? Put a voltmeter on the battery to see what it is charging to.

I'd want to know what the charging system is doing also. A cheap meter will give you enough info to know if you have a wiring issue or a charging issue. Good luck...

 

[Wombat125]

I'll check that out, but not for a few days. Inlaws are arriving tonight and we're in the middle of graduation season. I see my tractor play time dwindling away.

Dumb question, but what do you think I might see my charging system doing now? What should I see it doing if it were operating normally?

Thanks again for the advices.

 

[mfreund]

Operating normal with the tractor running at pto speed I would expect 13.7 to 14.2 volts. If it is overcharging anything above 15v.

Just for giggles have someone load test the battery and make sure it is good. If the battery had a dead cell the regulator would try to charge it, causing the generator to go to full charge.

 

[Wombat125]

The behavior was the same for the previous battery and for the new one I just installed, so I'm pretty sure that's not the problem.

I am anxious to get out and check the rate of charge.

Mfreund -- I grew up in eastern Iowa (Marion), so tell everyone there hi for me.

 

[mfreund]

I am about 45 minutes east of there on the Mississippi river. Quad Cities USA

 

[Wombat125]

A little update...

Per several of your suggestions, I put a meter on the battery to see what the charging system is doing. So here it is.

At slowest idle, the generator is putting out just barely over 12 volts. Then as I increase engine RPM, the charging voltage increases comensurately up to about 13.6 volts at about 80% throttle. Increase the throttle past 80% and the charging voltage abruptly drops back down to just over 12 volts. Once this voltage drop occurs it sticks there, regardless of what I do with the throttle thereafter.

So now what do y'all think?

Thanks!!