Ignition Switch

Step by step automotive guide on how an ignition switch and lock works, this article does not pertain to remote ignition keys.

Step 1 - An ignition key is used to add security to the vehicle by only allowing the possessor access to control a particular motor vehicle. This key is inserted into the lock tumbler of the switch, which include various key positions such as "ON", "START ENGINE" and "ACCESSORY".

Typical Ignition Switch

Step 2 - When the key is in the "ON" position, the vehicle's electrical system is energized without engaging the starter motor. To engage the starter motor the key must be momentarily positioned one additional increment which creates the initial engine rotation causing it to run. The accessory position which is located in the opposite direction of the "ON" position, is used when the user desires the use of an accessory such as the radio, this key position does not excite the engine or drive train electronics.

Key "ON"

Helpful Information

The ignition switch is constructed into separate pieces known as the tumbler and the electronic ignition switch itself. The tumbler is connected to the switch which is activated by the key. Some manufacturer's have integrated in additional security measure in the form of a frequency chip located inside the key itself, the vehicle must detect this chip to operate. Malfunctions of the ignition switch include: intermittent stalling, partial electrical system failure and complete vehicle shut down.


Written by
Co-Founder and CEO of
35 years in the automotive repair field, ASE Master Technician, Advanced Electrical and Mechanical Theory.


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