How to test rectifier 2006 road star

Check the diodes in your rectifier. Check the output voltage of the alternator.

what is your battery voltage? check for loose batter terminals and ground cables. Charge the battery if its low and then see if it will start. once its running test the voltage again. It should put out 13.5-15 volts just off idle. if it doesnt, something is wrong with your charging system.

Is your alternator putting out? Is your rectifier good? Test the alternator by checking the battery voltage when the engine is reving about 1200. Check the rectifier with a self powered test probe (engine off): If the light lights one direction but not the other - you are probably good. If it lights both directions or neither direction it is probably bad. A rectifier is suppose to pass 1/2 of the AC sine wave and not the other 1/2, creating 'rectified AC' which is used to charge the battery.