Troubleshooting Charging Issues

The charging system on my 6V system “TO-30” has quit. I have two related questions: How do I troubleshoot a generator system, and why should you not start the engine (as per the polarization procedure) before polarizing the generator? December 2, 2015.

Problems in the charging system have to be in either the battery, wiring, ammeter, voltage regulator or generator.

If you have replaced the battery, check that the positive terminal is connected to the ground strap, and the negative terminal is connected to the cable going to the starter switch. Make sure the other end of the ground strap is making a good connection to ground, in this case, the bolt on the back of the dash that secures the upper steering gear casting.

The condition of the ammeter should also be checked. Is the ammeter showing any movement when the ignition switch is turned on or the lights are turned on? If the distributor points are closed the needle should move slightly to the left or discharge side. Turning the lights on, if the tractor has lights, should cause the ammeter to move to discharge as well.

Once the tractor starts and is revved up enough for the cutout in the voltage regulator to close, it should move to the right or charge side. If there is no movement, it is possible the ammeter is bad in which case the generator will not charge.

The most common problem with these systems is the voltage regulator. A simple way to check the regulator is to temporarily ground the generator “F” field terminal by attaching a short jumper wire between the “F” terminal and ground. This will bypass the regulator and put the generator in the high charge mode. If the ammeter shows charge with the “F” terminal grounded with the jumper wire, the voltage regulator is bad and needs to be replaced.

There are other tests that can be performed if you have a Ferguson On the Farm Service Unit which has a combination volt meter/ammeter with a variable resistance load. With this instrument the voltage regulator, battery and generator can be tested and adjusted. Without that option you will have to take the generator and possibly the regulator to an automotive electrical repair facility, or starter alternator shop and have them bench tested.

You can use a voltage test along with the voltage regulator test I suggested. An increase in voltage at the battery between the not running and running state at or above 1,000 RPM would be the result of generator output. A similar test is part of the series run with the Ferguson On the Farm test unit.

The system should be polarized whenever the generator or regulator are disconnected. As I understand it, polarizing sets electricity flowing in the right direction which is essential for the generator to charge. Failure to do so can cause burned relay points in the voltage regulator, run down the battery or damage the generator.