JD 650 Battery Polarity Issue

[gurumanjohn]

I have a JD 650 (1986) that I bough last Spring. Recently, the battery got weak and my neighbor and I went to charge it on a trickle charger. We discovered to our surprise that it required a positive ground connection. I checked the JD 650 manual and it says clearly that the tractor is a negative ground. What's going on?

 

[Oaktree]

I had a 750 (basically same machine) and it was negative ground.

 

[gurumanjohn]

Oaktree - Thanks, the manual specifically said it's a negative ground. The question is: why did someone change it to positive ground? Moreover, it doesn't appear that the wires were moved. They probably just turned the battery around. I'm wondering if it can be reversed to its original negative ground or is it too late for that?

 

[CobyRupert]

Weird. One wouldn't think a "new" (1986) tractor would be positive ground, and the manual and others seem to confirm that. So, this has got me thinking: what happens if somebody puts battery in backwards? Nothing or is something else going on here? Not sure, but seems like the alternator and maybe the starter motor would object to reverse polarity, whereas other loads (lights, solnoids, etc..) don't care Your tractor hasn't been running backwards all these years has it? (joking)

 

[CobyRupert]

What does a dc voltmeter say when put on the old battery? Has the polarity of the battery been reversed from its markings? If that's even possible....

 

[Zebrafive]

What does a dc voltmeter say when put on the old battery? Has the polarity of the battery been reversed from its markings? If that's even possible....

My thought too. Maybe if dead and charged wrong it would no longer match it's markings.

 

[Xfaxman]

I have a JD 650 (1986) that I bough last Spring. Recently, the battery got weak and my neighbor and I went to charge it on a trickle charger. We discovered to our surprise that it required a positive ground connection. I checked the JD 650 manual and it says clearly that the tractor is a negative ground. What's going on?

How did you discover this?

I have read about batteries being reverse charged.

The battery posts are different diameters, so it isn't easy to reverse the cables accidentally.

 

[kebo]

Here's what I suggest.... find/beg/borrow a DVM (digital voltmeter) and set it to read DC volts. Put the red meter lead on what you *think* is the (+) positive terminal (marked) on the battery. Put the black lead on the other terminal, which should be the (-) negative (marked) terminal. The meter should measure +12.8 volts DC, or thereabouts. If you get a -12.8 volts DC on the meter, then the terminals have been marked wrong, or as mentioned it was reverse charged. NOT a good situation! I have owned two 750's myself, and as the other poster stated, they were both negative ground and the 650 should be similar.

 

[texas42]

I had a 1983 or so JD 750
It was a positive ground system

 

[Oldtink]

Oaktree - Thanks, the manual specifically said it's a negative ground. The question is: why did someone change it to positive ground? Moreover, it doesn't appear that the wires were moved. They probably just turned the battery around. I'm wondering if it can be reversed to its original negative ground or is it too late for that?

Your 650 is certainly negative ground.....and yes it sounds like the voltage regulator is toast also. Your alternator should put out 30 volts AC @ 2400 rpm to the regulator, (2 blue wires) On the regulator side of the attaching plug, black is ground, red is 12+ battery, green will swing + or - depending if it is charging or discharging and yellow is 12+ output to battery.