Today at Atelier Kaz - ex-Honda R&D, F1, Indy/CART engineer

The socket itself is designed as follows.

The metal shell acts as the GND point.

At the centre, there is a bimetal material acting as the Positive terminal.

It is fixed to the insulator with brass rivet (blue) and creating 2 fairly wide curved terminals (yellow).

These 2 terminals have certain spring character and being as bimetal, once it reaches certain high temperature, it will open up resulting in releasing the cigarette lighter body.

Most of the Japanese car manufactures will only supply the power to the cigarette lighter with IGSW in ACC and not through permanent battery voltage.







This photo shows how the 2 bimetal terminals locks the lighter unit (yellow line).

Separated by the white insulator, the rest of the round metal lighter body is connected to the GND side of the socket.

So, once the lighter gets really hot, the yellow line simply widens/opens up releasing the lighter body.









This is how the actual lighter body is engaged to the bimetal terminal.

The really hot lighter element won’t touch the centre terminal and there is an air gap.