Here's what my service manual says use this information at your peril:
The single phase charging system found on inline engines provides basic battery maintenance. Single Phase, full wave systems like these are found on a variety of products.
The charging system produces electricity by moving a magnet past a fixed coil. Alternating current is produced by this method. Since a battery cannot be charged by AC, the AC current produced by the lighting coil is rectified or changed into DC to charge the battery.
To control the charging rate an additional device called a regulator is used. When the battery voltage reaches 14.6 volts the regulator sends the excess current to ground, this prevents the battery from over charging.
The charging system consists of the following devices:
Flywheel containing magnets
The Lighting coil or alternator coil
The battery, fuse assembly and wiring
The lighting coil is usually a bright exposed copper wire with lacquer type coating, Lighting coils are built in with the ignition coils on some models and the whole assembly must be replaced.
In the charging system the rectifier/regulator is the most difficult item to trouble shoot. You can avoid troubleshooting the regulator/rectifier by checking around it.
Cheek the AC voltage output of the lighting coil, if the AC voltage is low check the charge coil for the correct resistance and insulation to ground.
If these check ok measure the resistance of the Black wire from the rectifier/regulator to ground for and for proper voltage output on the red wire coming from the rectifier/regulator to the battery. If all the above check with in specification replace the rectifier/regulator and verify the repair by performing a charge rate test.
A thorough, systematic approach to troubleshooting will pay big rewards; build your troubleshooting check list with the most likely offenders at the top.
Do not be tempted to throw parts at a problem with out systematically troubleshooting first.
1. Do a visual check of the wiring and fuses; Are there any new additions to the wiring? A good clue might be "Everything was working OK until I added that well Pump".
2. Test battery.. Well you have a new one..
3. Perform a fuse and red wire check with the voltmeter. Verify the ground at the rectifier. Do you have 12 volts and a good fuse? While you are at the Red wire, check the alternator output with an ammeter. Be sure the battery is down around 12 volts (not sure why)
4. Put a test lamp or ammeter inline with everything turned off and look for a draw.
5. The electrical system cannot keep up with demand. Do a consumption survey.
6. Go to the Source. Check the lighting coil for resistance and shorts to ground
7. If all these tests fail to pin point the problem and you have verified low or no output to the battery then replace the rectifier.
Donít blame me if you replace the rectifier and itís still not charging