no charge

For intermittent problems suspect worn brushes in the generator. You can verify that by measuring the voltage on the "Ground here to test" terminal on the back of the voltage regulator.

i would check that but this is the third altenator we put in inside of four months and get the same thing.had all of them tested and they come back as good

Still must diagnose with voltage measurements to see what is happening. When it acts up again, use an inexpensive digital voltmeter to measure the voltages on the wires that plug into the back of the generator. Yellow must have battery voltage all the time. Green / red should have around 2.0 volts and the battery light should be on when the ignition switch is turned to "run" but the engine isn't running. You should find near battery voltage on the green / red wire when the battery light is off and the engine is running. If the generator is working, you will measure around half of battery voltage on the white / black wire. In that case, measure the output wire too. Holler back with those readings.