Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Starter Motor: Design: Solenoid
The control solenoid has two functions. The first is to mechanically engage the pinion in the flange/flywheel gear collar. The other is to function as a relay and to handle the greater current required to drive the starter motor when the pinion engages with the gear collar.
The solenoid consists of the following components:
- Moving steel cores. Moved by pull-in winding in the solenoid, slides the pinion into position and moves the moving switch towards the fixed switches.
- Pull-in winding. Pull in the moving steel core. Disconnects when the moving steel core reaches the bottom position.
- Hold-in winding. Holds the moving steel core in position for as long as the solenoid is powered.
- Fixed steel cores. Stop position for the moving steel core.
- Contact spring
- Fixed contacts. Closes when the moving switches reach the fixed switches.
- Terminals. Two, one for the battery and one for the DC motor.
- Moving switch. Switch which closes the fixed switches.
- Moving shaft. Affected by the moving steel core and connects the moving switches to the fixed switches.
- Return spring. Resets the solenoid components to the rest position when the starter motor relay is disconnected.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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