Per painless wiring instructions * Under some circumstances the connection of the alternator will not allow the engine to be shut off. If this occurs a diode will need to be installed inline on wire #914. This will preventthe alternator from back feeding into the ignition system and thus causing the engine to run with the ignition switch turned off. The Radio Shackpart number for the diode is 276-1661. It is to be installed with the stripe towards the alternator.