1720 Alternator wiring problem

[jnhelton]

Anyone have a color-coded wiring diagram for the alternator on a 1720? I discovered I don't have a warning light for the alternator. In my investigation it turns out that 2 wires in the wire bundle within inches of the alternator aren't terminated. A white red striped with brown spots wire that goes back to the light. A white with brown spots (no stripe) that goes to the "L" terminal on the Alternator.
If I connect these, the light works perfect but the tractor won't stop running with the ignition switch off. The reason is that the "L" wire carries a constant 2 volt current when the alternator is spinning. This voltage bleeds back to the fuel stop solenoid and is just enough to keep it from shutting off.
HELP! Thanks

 

[JC-jetro]

Anyone have a color-coded wiring diagram for the alternator on a 1720? I discovered I don't have a warning light for the alternator. In my investigation it turns out that 2 wires in the wire bundle within inches of the alternator aren't terminated. A white red striped with brown spots wire that goes back to the light. A white with brown spots (no stripe) that goes to the "L" terminal on the Alternator.
If I connect these, the light works perfect but the tractor won't stop running with the ignition switch off. The reason is that the "L" wire carries a constant 2 volt current when the alternator is spinning. This voltage bleeds back to the fuel stop solenoid and is just enough to keep it from shutting off.
HELP! Thanks

Closest thing I have is for 1710. I don't know how close it is to 1720. It just might give your some clue. please look at the attached PDF.

JC,

 

[jinman]

JC, it appears from your diagram that you have an external VR and the OP has a VR internally in his alternator from his description of the wires. Don't know. . .

 

[jnhelton]

Thanks to both of you. Didn't know this is the quick way to reply. Yes I have an internal VR. Can anyone say whether or not the 'L' terminal should be putting out the 2 volts constantly? Thanks

 

[jinman]

Jnhelton, I answered your PM. Without the diagram, I think there is an isolation diode missing, bypassed, or shorted. My tractor has an isolation diode to keep any postive voltage from feeding back and powering the bus through the light.

 

[JC-jetro]

JC, it appears from your diagram that you have an external VR and the OP has a VR internally in his alternator from his description of the wires. Don't know. . .

Yes Jim, You're right. I do have External VR on my 1700. The diagram I posted was for Ford 1710 rather than 1720. That was the closest thing I had on my IT FO-44. I thought it might help the OP some.

JC,

 

[jinman]

Yes Jim, You're right. I do have External VR on my 1700. The diagram I posted was for Ford 1710 rather than 1720. That was the closest thing I had on my IT FO-44. I thought it might help the OP some.

JC,

Well your diagram does show the light "L" lead from the external regulator. It's wired pretty much like mine and others with internal regulators, but I have an isolation diode after the light between it and the bus. I'm not sure of the symbology on your diagram, but I didn't see anything like that.

 

[jnhelton]

I'm betting you're right jinman. This isolation diode is in the internal IC circuit right? I think the original owner cut the wire rather than fix it!?

 

[jinman]

I'm betting you're right jinman. This isolation diode is in the internal IC circuit right? I think the original owner cut the wire rather than fix it!?

I think you could put one inline. Just make sure the negative end is turned toward the alternator's "L" output. That way it will allow normal current to illuminate the light and isolate the circuit when the key is turned off.

EDIT: I just changed the word above to "negative." I don't know what made me type positive the first time. Must be old age.

 

[Jbrink64]

Anyone have a color-coded wiring diagram for the alternator on a 1720? I discovered I don't have a warning light for the alternator. In my investigation it turns out that 2 wires in the wire bundle within inches of the alternator aren't terminated. A white red striped with brown spots wire that goes back to the light. A white with brown spots (no stripe) that goes to the "L" terminal on the Alternator.
If I connect these, the light works perfect but the tractor won't stop running with the ignition switch off. The reason is that the "L" wire carries a constant 2 volt current when the alternator is spinning. This voltage bleeds back to the fuel stop solenoid and is just enough to keep it from shutting off.
HELP! Thanks

There is a diode on that circuit, it is available through NH, PN SBA385620220