Cigarette Lighter: Description and Operation

Voltage is present at a contact inside the Cigar Lighter socket, through the AUDIO Fuse at all times. The Cigar Lighter socket shell is grounded at all times.

Whenever the Cigar Lighter is in its socket, one end of the Cigar Lighter coil touches the socket shell and is grounded. Pushing the Cigar Lighter into the socket causes the other end of the Cigar Lighter coil to touch the "hot" contact. Current flows through the AUDIO Fuse and the Cigar Lighter coil to ground, causing the coil to heat up.