Generally the heater shorts out because water is dripping from above, it comes from the pollen filter area, the heater matrix is lower down, so doesn't usually cause any electrical problems when its dripping, except for giving you a wet foot (or a burnt foot if it decides to burst during an epic head gasket failure as i found out)

It doesn't mean its not leaking, but i wouldn't link the two, if its loosing water, checked the bottom right corner of the radiator, then the two Bakelite type flanges on the cylinder head, and make sure the coolant bottle cap allowing pressure to escape, then try to get your hands up under the dash and have a poke about for any wetness from the bottom of the blower housing.