Starter motor protection system

A starter for an internal combustion engine having a ring gear, the starter including:

• a starter switch, operable between an open and closed condition, adapted to be electrically connected to an electrical power source;
• a pinion adapted to be axially movable into and out of meshing engagement with the ring gear;
• a plunger for moving said pinion toward said ring gear and having a movable contact at one end thereof;
• first and second stationary contacts both so positioned as to be contacted by said movable contact, said first stationary contact being electrically connected to said electrical power source;
• exciting coil means for moving said plunger toward first and second stationary contacts, said exciting coil means comprising a holding coil and an attracting coil, said holding and attracting coils having windings electrically connected in series with one other and having a connection coupled thereto at respective one ends of said holding and attracting coils;
• a relay including;
• (a) a pair of normally open contacts connected in series to said electrical power source and said connection coupling said windings of said holding and attracting coils, and, (b) a relay coil electrically connected in series to said starter switch and the other end of said holding coil, and which is energized when said starter switch is turned on, to thereby close said normally open contacts;
• a starter motor, said starter motor being drivingly connected to said pinion;
• means for electrically connecting said second stationary contact to said starter motor when said starter switch is closed, whereby, when said first movable contact is moved into contact with said first and second stationary contacts to electrically connect them together, said starter motor will be energized by said electrical power source;
• a motor controller comprising:
• means for determining the voltage at said first stationary contact;
• means for determining the voltage at said second stationary contact;
• means for calculating the voltage difference between said first stationary contact and said second stationary contact;
• means for comparing said calculated voltage difference to a predetermined reference voltage differential, and, if the calculated voltage differential is not less than or equal to said predetermined reference voltage differential interrupting the power supply to said relay coil.