04 john deere charging bafflement

Joe Cannon · Feb 14, 2018

OK the alternator is working properly and the regulator is also but it is not charging the battery..
There is a connector (under the dash) that I get 13.2 volts or so out of and 11 .whatever on the other side of it (battery voltage) when I check each side ..(unplugged of course )
There is also a small diode plugged into the wiring harness that I can find on any diagrams but it reads really odd on continuity on my meter ..I am not even sure what it is there for...It reads 0 in one direction and 50 in the other ..
any ideas befor I rip the wiring harness out and start over?

3Lfarms · Feb 15, 2018

That wire has a diode in it so current can only flow one direction.
Some charging/ignition systems require it. If you take it out, the alternator will supply power to your ignition and when you turn off the key, the engine may continue to run.

3Lfarms · Feb 15, 2018

How old is the battery? That is the place to start with problems like this.
What is the battery voltage before starting, with engine idling, and at PTO speed? Those numbers will tell us whether the alternator is charging or not.

Joe Cannon · Feb 15, 2018

3Lfarms said:
How old is the battery? That is the place to start with problems like this.
What is the battery voltage before starting, with engine idling, and at PTO speed? Those numbers will tell us whether the alternator is charging or not.

Just so you know ..I am an extra class ham radio operator (not bragging just so you know I know how to use test equipment etc.)
The thing that really confuses me is a connector that has like 8 gauge wire going to it..
If I uncouple the connector ..one side reads 13+ volts (common sense would say that is the output from the regulator)
The other side of the connector is the same as the battery voltage..
If you connect a amp meter from the 13+ volt side (no current) it will not even light a test light..
If you put a amp meter between the two (13+ volt side and the side that is reading battery voltage no current ) I even put my test lamp between the two ..no go
You would think that that would be the wire that monitors the battery voltage (if so why such a large gauge wire)
I am about to tear the whole wiring harness apart and trace every wire..
I know its something stupid that I am blind too..
The person I bought this tractor from replaced the motor and battery ..it could be as simple as a ground wire that was not replaced ...
Any ideas????Thanks

DwayneB · Feb 15, 2018

From what you described I'd jump that one wire across the connector. Sounds like a bad connection.

DwayneB · Feb 15, 2018

DwayneB said:
From what you described I'd jump that one wire across the connector. Sounds like a bad connection.

If the output of the alternator is 13v that 13v has to get to the battery.

Sparkynutz · Feb 15, 2018

Not sure what your model is but I have a John deere sst16 hydrostatic zero turn. The steering started acting up something fierce but mainly when I reverse. It got so bad over about a year worth of mowing I couldn't even mow with it. I changed hydro oil and nobody at deere dealer had a clue. After searching online I came across a single thread of steering not working due to low voltage. I installed a voltage meter to watch while mowing and the voltage was over 12 most of the time. Enough to start and run just fine then if I reversed it would drop down to 7-8v steering wouldn't work then it would go right back up. Obviously it was charging or my battery would have been long dead but something with reverse must have put a larger draw on it that was only visible when reversing. I replaced the battery but what fixed it was when I replaced a black box looking thing with a couple wires on it. I think it was voltage regulator. It was only $14 shipped from amazon. Part # wasn't right but it said it was compatible. Obviously it was because that was about 3 years ago and I havent had a single steering problem since. Your issue may be totally different but might be worth just trying to see if that's it.
Good luck!

CobyRupert · Feb 15, 2018

So you’re getting 11 volts at the battery? When not running? This would be typical of a battery with a bad cell. Can you check specific gravity of each cell?

kthompson · Feb 15, 2018

Not same as your case but I cranked my JD about a month back, first time in about two months of for us record setting cold period in there. Cranked right up fine and I drove it to shop to work on mower on it. When I went to crank it the second time only had a single click. Tried jumper, battery charger on it over night showing it was charging and volt meter showed voltage on battery was a full 12 volts after charger was removed but again all it did when trying to start was single click. Finally took battery to have it tested, only tested at about 66% of its amps while voltage was good. Replaced battery and no more issues. Voltmeter could not test the battery fully.