Delco 24 volt generator polarizing

[joefarm1]

I have a John Deere 4020 diesel with the original 24 volt generator (Delco 1103026). The generator had an open field coil. After replacing the field coil, the generator will not generate voltage when isolated from the voltage regulator, tractor running, A2 to +24v, A1 to -24v, A2 to F.

With the belt removed, A2 to +24v, A1 to -24v, the generator motors opposite normal rotation. I have tried polarizing with no change. I have reversed the field coil connections with no change. I have tried reversing the test voltage to A1 and A2 with no change in rotation direction.

This generator did not work when I purchased the tractor. What is causing the generator to motor in reverse?

 

[Tx Jim]

JD 24 volt starting/charging system is neither + or - ground but is insulated from tractor frame.

 

[joefarm1]

If I connect the “generator test” setup, the voltmeter remains at 0 volts.

 

[Tx Jim]

IE you have no voltage between generator post A1 & A2 with wiring harness attached & regulator has been polarized according to 2nd photo? Does your tractor have 2 circuit breakers mounted on a plate by starter?

 

[joefarm1]

JD 24 volt starting/charging system is neither + or - ground but is insulated from tractor frame.

Thanks for the reply. I am aware that the generator is not grounded. The generator is not producing a measurable voltage if I perform the “generator test”. The new field coil draws 0.77 amp with 24v applied across A1 to F which is acceptable in the JD service manual. I believe the armature is good since the generator motors when 24v is applied A2 to A1. Everything that I have read suggests the generator should motor in the same direction as normal rotation when 24v is applied A2 to A1. This is not the case.

 

[joefarm1]

IE you have no voltage between generator post A1 & A2 with wiring harness attached & regulator has been polarized according to 2nd photo? Does your tractor have 2 circuit breakers mounted on a plate by starter?

A2 is connected to the + side of 24v. A1 goes to the “GEN” terminal of regulator. “BAT” is connected to the - side of 24v. When I touch the jumper to the regulator terminals, I get a spark, and the generator has 24v applied across A2 to A1. I do not see a plate with circuit breakers by the starter.

 

[Tx Jim]

After you get tired of attempting to get 24 volt system operating correctly I suggest to consider changing your tractor over to a 12 volt system with a 12 volt gear reduction starter & alternator. 12 volt starters & batteries are much more powerful today than 50+ yrs ago. 12 volt electrical system makes ones life much more simple when compared to JD's unique 24 volt electrical system. 12 volt system also offers less chance for fire caused by electrical wiring malfunction.