NAA 12 Volt conversion issues

[michaelud]

Hello,
At beginning of Sep I converted to 12 volt neg ground from 6 vold neg ground. Bought conversion kit from farmtractorrepair.

Made all connections except missed connecting black (ground) wire from key to terminal block. I connected red battery cable to positive battery post. When I touched the negative cable to the negative post there was a big spark. [b:a51e708dd9]Why did that happen?[/b:a51e708dd9]

Tractor would turn over but not start. I took a slower look and discovered the missed connection from the key. Made the connection and the tractor fired and ran great. This was at beginning of Sept.

Now, my son starts the tractor drives it around the farm but then it dies. Full of gas. Must be spark I figure. New alternator with one wire. Ammeter not functioning so I will buy a new one.

Yesterday my son starts the tractor, drives it around the place, but then the tractor stops running and won't start. The tank is full of fresh gas; carb resently rebuilt. I wonder whether the new battery is not being charged by the alternator because the spark at initial connect burnt or destroyed something. [b:a51e708dd9]Any thoughts on what the problem could be?[/b:a51e708dd9]

Thanks

 

[J Hamilton]

That big spark may have ruined your
alternator, I would have that tested. Also
with a one wire alternator you need to speed
the engine up to excite the alternator to
make it charge. Do you have a multimeter?

 

[michaelud]

(quoted from post at 04:55:08 09/11/22) That big spark may have ruined your
alternator, I would have that tested. Also
with a one wire alternator you need to speed
the engine up to excite the alternator to
make it charge. Do you have a multimeter?

I suspect that the alternator (brand new) is shot. Dang.

I do have a multimeter.

 

[JMOR]

" black (ground) wire from key to terminal block" There ya go! Sounds like cause enough for a big spark! :idea:

 

[Steve@Advance]

I can't envision a ground wire being connected to the ignition switch. None
of the terminals would ever be connected to a ground!

The spark on connection of the battery may have blown a connection open, or
internally blown the amp meter. But if the amp meter is open internally, and
is wired correctly, there should be no power to anything.

I don't see an initial short as being harmful to the alternator. What harms
alternators is connecting the battery or jumper cables backward, or trying to
charge a dead or shorted battery with the alternator.

Do you have battery voltage to the BAT post of the alternator? On a 'one
wire', that is all that is needed, and a fast enough spin to initiate the
charge.

 

[michaelud]

My knowledge of electrical systems in general is just enough to get me into trouble, and that's where I am now with my tractor.

The ignition key has two wires coming out of it: a yellow and a black. Both connect to the teminal block. I overlooked connecting the black wire to the terminal block. Thinking that all wires had been properly connected, I connected the positive battery cable to the positive post and then when the negative cable touched the negative post the spark occured.

I stepped back, thought a bit about why that may have happened. When we bought the tractor in the early 80's it was negative ground. It ran somewhat reliably for many, many years as 6 volt negative ground. So, I knew the grounding wasn't reversed. I then touched the negative cable to the negative post. No spark. The tractor cranked over but didn't start. I looked closely at all the wiring and noticed that the black wire from the ignition key (which I assumed is a ground wire) was not connected to the terminal block. After the wire was connected the tractor fired right up an ran like a champ.

I broke the brand new ammeter during the install. The old ammeter didn't work when connected to the wires as directed by the instructions. So I don't know if the alternator is working. Prior to connecting to the battery, I used a multimeter to test continuity from the alternator to the ammeter (which was broken). The multimeter showed resistance (ohms) indicating to me that I had connected the correct wire from the alternator to the ammeter.

So, when my son started and drove the tractor it performed well for a period of time and then died. He said it would not crank over after that. It seems to me that the alternator is/was not charging the battery and the new battery simply ran out of charge. I will take another very close look at all the connections to verify all is connected as it should be. But the tractor did run.

Why the initial spark when connecting the negative battery cable and then no spark when connecting the negative ground is puzzling. Any thoughts would be appreciated.

 

[JMOR]

"(which I assumed is a ground wire)". Bad assumption. One switch wire is battery voltage and the other is switched battery voltage.

This post was edited by JMOR on 09/12/2022 at 10:04 am.

 

[michaelud]

Thanks for the schematics.

There was no smoke from the alternator. But apparently it is not charging the battery. Why not?

Another question: the wire from the alternator is supposed to be connected to the "+" of the ammeter. What would happen if it were connected to the "-" of the ammeter?

PS: I hate electrical problems.

 

[JMOR]

(quoted from post at 16:12:22 09/12/22)
Thanks for the schematics.

There was no smoke from the alternator. But apparently it is not charging the battery. Why not?

Another question: the wire from the alternator is supposed to be connected to the "+" of the ammeter. What would happen if it were connected to the "-" of the ammeter?

PS: I hate electrical problems.

f swap terminals on ammeter, it will reverse the readings, i.e., if charging current going into battery shows + (charging) reading and you swap, then charging current going into battery will show a - (discharge) reading.
Note that the one and only wire on that - (negative) terminal is connected to battery, via solenoid terminal with battery cable. No other connections to this ammeter terminal. If alt is connected here, then ammeter won't read alt output. All loads and alt connect to the other ammeter terminal.

 

[michaelud]

Update: I jumped the tractor and she fired up. When I disconnected the jumper cables she sputtered and died. I could not get her going again.

I pulled the battery and alternator and have them here at my house. (The tractor is 80 miles north of me on an island. The property where the tractor is located is off grid.)

I will test the alternator. The battery is on the charger.

Something was pulling power when I connected the battery. At this point I haven't got a clue what was pulling power.