These switches are used to turn on the reverse lights to illuminate the back area during manoeuvring, for example, for parking the car. Equipped with tip seal with flap of mineral oil on the driver's side and  a shielded from the rain on the clamp side.

 

Constitutive elements and operating principles

The Back Lights switches are made of a metal body, a metallic tip  and a plastic housing. They are operated by a cam mounted on the gear shift.

The metal body is provided with a threaded end on which is provided a hole to allow the push rod to slide through mechanical movement of the shaft of the gearbox. The threaded part can be equipped with a metal gasket or an o-ring to ensure a watertight seal.

On the metallic body there is a beaded plastic case in which pins or blades of connection are planted.

The internal elements of the device are protected from the oil thanks to a membrane in fluorine elastomer or nitrile. The force exerted by the tip deforms the membrane and activates the disc or contact of the movable plate, opening / closing the switch.

 

Major causes of failure

  - Accelerated wear caused by cycles performed at high and low temperatures.

  - Deformation of the casing with respect to the metal body of the switch

 

Effects of failure

  - Progressive degradation of the switch through wear

  - Loss of tightness

 

The reversing light switches  normally have two terminals, but can be formed by four or more terminals.

They may include:

  - 1 circuit N / O  normally open - the switch is closed by the contact between the slats of connection and the mobile disk of contact, acting on the tip and the disc moves the circuit closes.

  - 1 circuit N / C normally closed - the switch is closed by the contact between the slats of connection via the mobile plate, acting on the tip plate moves, and the circuit opens

  - 2 circuits, one of which is N/O and the other N/C

  - 3 or more circuits exchanging the circuit on a straight drive diversified and to identify the type of gear.