Ford Mustang Service Manual: Relay Switch

Starting System (Description and Operation)

Starter Motor

The starter motor is a 12-volt unit that has the starter solenoid mounted on the drive end housing and functions as follows:

  • The current flows through the solenoid energizing coil until the solenoid plunger is at the end of its travel.
  • The plunger closes a set of contacts that bypass the energizing coil, letting the holding coil keep the starter drive engaged and passing starting current to the starter motor.
  • The motor is energized when the starter solenoid contacts are closed.
  • The starter drive engages the flywheel ring gear and starts the engine.
  • An overrunning clutch in the starter drive protects the starter motor from excessive speed when the engine starts.

Starter Relay

The starter interrupt relay consists of:

  • pull in coil and contacts
  • When the ignition switch is in the START position:
  • the pull-in coil is activated and pulls the contacts together.
  • current passes through the starter relay from the engine compartment power distribution box to the starter solenoid.

Clutch Pedal Position (CPP) Switch

The CPP switch for:

  • a manual transmission closes when the clutch pedal is depressed, completing the starting circuit.
  • an automatic transmission is a jumper inserted in place of the CPP switch to complete the circuit.

Starter System - Operation

When the ignition switch is turned to the START position the starter relay switches power to the starter solenoid causing the starter motor to engage as long as:

  • the clutch pedal is depressed (manual transmission only).
  • the digital transmission range (TR) sensor is in PARK or NEUTRAL (automatic transmission only).
    Starter Drive and Flywheel Ring Gear Inspection
    Starting System (Description and Operation) Starter Motor The starter motor is a 12-volt unit that has the starter solenoid mounted on the drive end housing and functions as follows: The current fl ...

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