1964 JD 4020 diesel 12 conversion not starting problem

[steveinohio]

On my 1964 JD 4020 diesel in April, 2020 I had an A & I 12 volt conversion from 24 volts to 12 volts installed. It has worked fine with no problems since last Friday afternoon I went to start it, the starter was cranking the engine as but slowed down and almost stopped as if the batteries needed charging. I found on the left side battery the positive post was heavily corroded so I clean all the posts and battery ends for both batteries. When I went to try to start it only the relay (mine is fastened to the lower dash panel by the floorboard) would be clicking as long as you held the key on but would not turn over the starter. I checked the batteries with a load tester and both showed 11 volts under load. (New batteries were installed in August, 2018) I have dash lights, fender lights, fuel gauge that come on. The transmission lever has always been in PARK so I don't think that may be an issue. I ran a jumper cable directly from the positive post from the batteries and grounded the starter and all it does is display a small spark without engaging the starter. The starter is removed and I can turn the bendix and starter by hand. At this point my intention is to have the batteries retested and take the starter to a shop for their testing. Has anyone experienced the issues I 'm having? This conversion kit also has two small circuit breakers attached near the relay. Any and all assistance is always appreciated.

 

[Tx Jim]

Check to be sure both negative battery cables have good connection between cable & tractor frame. When you state batteries tested 11 volts under load were you checking battery voltage with starter engaged? Were batteries checked separately with other battery disconnected? If both batteries are connected to tractor electrical system then in reality you're only receiving reading from the highest voltage battery.

 

[used red MN]

Check the physical connection of cable ends to cables by trying to pull them apart. Give them a good tug like your pulling the head off a snake.

 

[steveinohio]

Check to be sure both negative battery cables have good connection between cable & tractor frame. When you state batteries tested 11 volts under load were you checking battery voltage with starter engaged? Were batteries checked separately with other battery disconnected? If both batteries are connected to tractor electrical system then in reality you're only receiving reading from the highest voltage battery.

Thank you for your reply. I removed the starter and took it to a local Auto Electrical shop. They bench tested it and could not get it engage or run. I will getting a new starter at the end of this week or first of next week. When using my load tester, I checked each battery individually.

 

[8850dave]

Do both positive cables run directly to the starter, I had a 12 volt convesrion that the right battery cable connected to the left battery but had a very poor connection, got longer cable and ran it to the starter and and a much better starter speed.