75 Ford 2000 Gas 3 Cylinder 12V - Warning Light On

OvrDEdge

New User
I bought this tractor a years or so ago and the only electrical thing on it that worked was that it cranked. I changed the oil and used it through the work season last year. During my time off for this Christmas i had a goal to fix all the electrical issues on it and made a bit of progress. The dash was new from the guy i bought it from since he tried to fix these problems too but wasn't successful. Other than that, i have replaced the wiring harness, tach cable, the water temp sender, oil pressure sender, dash voltage stabilizer (one of the terminals was broke off), head lights, and now the control box/regulator. One of my remaining issues is the warning light is on (the other issue is the gas gauge only works half the time). From suggestions I've seen on this site (and others from Google), I've done this testing:
- Engine running, voltmeter black cable to negative battery and red cable to field terminal directly on generator and i get < 1 volt.
- Engine running, voltmeter black cable to negative battery and red cable to D terminal directly on generator and i get < 3 volts. (What does the D stand for?)
From this behavior, i found an internet discussion that said i needed to polarize the generator so i unplugged the field terminal from the regulator and tapped it a few time to the battery positive terminal to get sparks. Plugged everything back in and did the same tests again and got the same results.
Next i found a discussion, that said to prove generator is good and regulator is bad, i needed to jumper from the positive battery terminal to the field terminal on generator. So, i unplugged the field line from the control box and jumper from positive battery terminal to the field line to the generator. After that i did the same test and got these results.
- Engine running, voltmeter black cable to negative battery and red cable to field terminal directly on generator and it was bouncing from 9 to 12 volts.
- Engine running, voltmeter black cable to negative battery and red cable to D terminal directly on generator and it was ranging from 11 to 13 volts.
At this point, the warning light was off and I figured that i needed to replace the control box. Ordered one that came in today but after replacing it, the warning light was still on. I did the same tests as above and got the same results (barely any voltage, then bypass field line and get correct voltage). Next I left the tractor running and hooked the field line back up to the regulator. I was about to cut the tractor off and noticed the warning light was off. The weird thing is it ran like this for a few minutes and by the time i was excited that it resolved itself and was going to button everything back up, the warning light came back on and the tests results were back to the original behavior.

Does anyone have any ideas what I'm missing?

This post was edited by OvrDEdge on 01/10/2023 at 04:40 pm.
 
Which warning light is coming on?
Oil pressure or generator?
You can monkey with your wires till the
cows come home but if it is your oil
pressure light...
 
The generator light. When I replaced the wiring harness I traced and toned every cable in the original and new. Then labeled them all. For the few cables that weren t plugged in or were broken, I used the manuals to figure out what goes where and labeled them appropriately as well and then hooked everything back up. This specific light connects to the WL on the regulator.

Thanks,
-J
 
Had several 1000 series tractors over the years and the gen light often will come on at idle. Means there is not enough current being produced at low rpms. Give them a bit of throttle and the light goes out. Just a suggestion.
 
That was an excellent idea! I went and cranked it this morning after i dropped the kid at school and the generator warning light went off almost immediately after it started. It was running at about 1000rpm at the time. It ran for about 30 seconds and the light came back on. My current working theory is that everything is working fine and I just need to leave the old girl alone. What I mean is that the generator charges back up to the correct voltage and then cuts out. While the generator is cut out, the warning light is on but once the voltage dips enough to reengage the generator, the light may come back on again. To prove this theory, I think I'm going to need to work it a bit. Does this sound like a good theory or am I off my rocker?
 
That is not normal behavior. That light bulb is effectively across the cut out contacts. Contacts closed, bulb shorted across, light out. Contacts open, short removed, current flow thru bulb & light. The on/off/on regulation function is in the voltage regulator portion of the VR unit and does not control the light. Once gen up to enough speed to pass the threshold to close cut out contacts, they remain closed until shut down, even if gen output drops below the pull-in threshold.... The drop out threshold is lower.
 
Well, at this point, the only thing that i haven't replaced is the generator. Are you saying i should have just bit the bullet and done the alternator swap?
 
You could have... loose connections or bad connectors and bad wires... Or bad brushes in the generator, or bad ground on the generator or regulator... all are possible.

But I find the replacement regulators, made in India, are mostly junk. It would seem that I see 2 out of 5 are bad. And the regulator is the number one failure point on the charging system. I do see the 2nd most failure is the generator. Once in a while a good wack with a hammer near the back end of the generator will knock the brushes loose, but if the generator does not go to full charge when you put positive on the field lead, its usually a dead duck. And since I usually go through 10 to 20 tractors a year, its sometimes both are bad.

And even though you dont need to polarize a new regulator, sometimes you need to polarize the generator one time, to get the regulator to wake up. This will restore a weak magnetic field in the field shoes to help the regulator kick in the first time although its not common for the shoes to loose their magnetic field.
 
I have a similar vintage tractor that had a lot of electrical challenges. One thing I discovered was that the fuse block was making intermittent contact. Once I fixed that, the charging system (alternator in my case) started working properly. Might be worth a look-see. Also, check to see that the generator light bulb is the correct number. Along the way it might have been replaced with something that fit the bulb socket. Just a thought.
 

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