[Morris]

On a charge light on the dash.....one side goes to the battery via the ignition switch (12 volts) which is 12 volts.....the other side of the lamp .....goes to the alternator which is close to the same on both sides of the lamp putting out 13.5-14.5 volts....which means the lamp will not light because the potential is the same on both sides of the lamp......if the voltage from the battery or the alternator starts to fail....then the difference in potential gets larger and the lamp starts to light.....the brightness of the light depends on the amount of voltage difference between the two sides of the lamp.....it at least warns you that something is not working properly in your electrical supply system....I doubt that the fuel pump had any effect on the Battery/Alternator lamp or supply.