JD 1520 Alternator sporadic Charging Voltage

   / JD 1520 Alternator sporadic Charging Voltage #1  


New member
Sep 12, 2021
John Deere 1520
Hello, Done a lot of reading but never posted. Hoping someone can help out.

I have a JD 1520 that just died one day. The points were getting very hot. We decided to put electronic ignition in it after we had to put a new ignition in it the went bad. Up and running but with the EI in it wasn't charging the battery. We weren't getting any voltage much over 12.4V from the alternator so I thought it was bad. We intended to get a single wire unit but matching up the pulleys was the problem. They tested my old alternator and it tested good. So we figured the voltage regulator was bad, and the wiring on this 1968 has been overheated and shows signs of wear. So the alternator fellas put a new side on the old one as the ear broke when I loosened it. To bypass the original VR and wiring they put a small rectangular VR on this one, and all I had to do was install, and run a wire from the big stud on the alternator to the starting wire on the solenoid. Belt is tight, pulling spins freely and does not appear to be slipping at all.

Put my meter on the battery posts while running and the meter fluctuates constantly from 2-14.85 volts. The wire I used was 12ga. I measured from the stud to ground and it fluctuates as well right at the alternator. Just to double check I took 4ga jumper cables and clipped form the alternator stud to the pos battery terminal, same fluctuation.

Home now, 75 miles from tractor. From what I read, double check the negative ground from the battery to the frame first.
If that doesn't do it, bad voltage regulator? Any tests I can do? I appreciate any help.

   / JD 1520 Alternator sporadic Charging Voltage #2  
It sounds like varying DC or you have AC ripple on the line. If the battery is properly connected you should see no variation. Try cleaning battery terminals and insides of connectors. Tighten connectors securely. Follow ground lead to frame. Clean and tighten there as well. Rerun your voltage tests.
   / JD 1520 Alternator sporadic Charging Voltage #3  
Welcome to TBN
If negative battery cable is still attached to battery box I recommend to relocate it to starter mounting bolt or engine block.