Charging Problem

allisbchal · Apr 25, 2018

1951 Allis B. Generator seems to be charging right, and according to wiring diagram all is wired right, but Ammeter shows that it is discharging. Checked cut out, seemed to be fine but got a new one of those too. Again, all hooked up right but still shows discharging.

Could it be resistor on the switch or what could possibly be the issue. Really puzzled here...

Thanks for the help!

Goose · Apr 25, 2018

The battery cables didn't get reversed, did they?

allisbchal · Apr 25, 2018

(quoted from post at 18:46:15 04/25/18) The battery cables didn't get reversed, did they?

No sir. Positive ground 6V system, by the way.

Bob · Apr 25, 2018

Check the VOLTAGE, a "6 Volt" system should be at about 7.4 Volts when running/charging.

If that's OK, your Ammeter is connected backwards for the choice of battery polarity.

Also, the connection to the BATTERY should be on one post of the Ammeter, and the output from the generator and ALL electrical loads on the other post.

steve(ill) · Apr 25, 2018

If you have checked and the generator is actually putting out over 6 volts, then just switch the two wires on the amp meter.

allisbchal · Apr 25, 2018

Should the generator be putting out a -7.4 or just normal 7.4? since it’s a positive ground... I just wonder.

YTSupport · Apr 25, 2018

The resistor guess is possibly a good one. Check out this article because it discusses how your generator kicks up it's charge by grounding the third brush. The resistor light switch is all about
controlling that third brush and the charge.

http://www.yesterdaystractors.com/articles/artint4.htm

tractorguy2 · Apr 25, 2018

Any chance the wires on the amp meter have been reversed? That
will cause the meter to show discharge when it is really
charging.

allisbchal · Apr 25, 2018

(quoted from post at 21:09:15 04/25/18) Any chance the wires on the amp meter have been reversed? That
will cause the meter to show discharge when it is really
charging.

Had thought that too...checked them with the wiring diagram and they’re right. Now, I don’t know if this changes things but it WAS charging, then it’s started discharging. Again, the Generator is charging the cut out seems to be working. Could that still be linked back to the resistor?

rvirgil_KS · Apr 26, 2018

"Should the generator be putting out a -7.4 or just normal 7.4? since it’s a positive ground... I just wonder.

If you connect your meter with black (-) lead to frame ground (as we usually now do by habit) and positive (+) lead to generator output , positive ground system should show negative voltage on a digital volt meter. Don't be surprised if digital meter gives erratic reading when tractor is running.

If using an analog meter (0 at extreme left of needle scale) the negative voltage will try to force meter against 0 stop and give no reading. You will need to connect red lead to frame and black lead to generator output to get a reading. But remember that since the leads are reversed you have a negative voltage.

allisbchal · Apr 26, 2018

(quoted from post at 07:19:19 04/26/18) "Should the generator be putting out a -7.4 or just normal 7.4? since it’s a positive ground... I just wonder.

If you connect your meter with black (-) lead to frame ground (as we usually now do by habit) and positive (+) lead to generator output , positive ground system should show negative voltage on a digital volt meter. Don't be surprised if digital meter gives erratic reading when tractor is running.

If using an analog meter (0 at extreme left of needle scale) the negative voltage will try to force meter against 0 stop and give no reading. You will need to connect red lead to frame and black lead to generator output to get a reading. But remember that since the leads are reversed you have a negative voltage.

Okay! Good! That’s correct then. Now, I’m thinking it may be the resistor on the light switch...

rvirgil_KS · Apr 26, 2018

Ground the Field terminal on the generator. If that makes it show charge your problem is somewhere from Field post back through the wire and the resistor to ground.

If still no charge, leave the Field post grounded and jumper across the cut-out relay. If it now charges you have a bad cut-out relay. If still no charge you have a generator problem. Also make sure generator belt is tight.

allisbchal · Apr 27, 2018

(quoted from post at 09:59:07 04/26/18) Ground the Field terminal on the generator. If that makes it show charge your problem is somewhere from Field post back through the wire and the resistor to ground.

If still no charge, leave the Field post grounded and jumper across the cut-out relay. If it now charges you have a bad cut-out relay. If still no charge you have a generator problem. Also make sure generator belt is tight.

Can anyone tell me what kind of resistor is on the B? I can order one of course but I wondered if anyone knew specs on it...

YTSupport · Apr 27, 2018

I looked in the shop tonight to see if I had a spare loose. I didn't. If yours is out, you can put a digital VOM on Ohms and measure it. I may be thinking of the Farmall, but I recall there being two positions. All the way out, is shorted to ground for full charge, then two levels of resistance (closed and one click out). If true, you'll measure it pushed in, then one click out. You might verify whether the third position is grounded or not. Again, this is from a poor memory, but if your switch is completely open, I think you might show discharge. You probably already tried pulling it out to force high charge?

There is a possibility I have that backward and hopefully someone will correct if so.

Charging Problem

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