Interior Lights

Interior lighting includes courtesy lights, map lights, and instrument panel lights.

Courtesy Lights

Courtesy lights using ground side switches

FIGURE. Courtesy lights using ground side switches.

Courtesy lights illuminate the vehicle’s interior when the doors are open. Courtesy lights operate from the headlight and door switches and receive their power source directly from a fused battery connection. The switches can be either ground switch circuit or insulated switch circuit design. In the insulated switch circuit, the switch is used as the power relay to the lights. In the grounded switch circuit, the switch controls the grounding portion of the circuit for the lights. The courtesy lights may also be activated by the headlight switch. When the headlight switch knob is turned to the extreme counterclockwise position, the contacts in the switch close and complete the circuit.

Courtesy lights using insulated side switches

FIGURE. Courtesy lights using insulated side switches.

Reading and Map Lights

Individual switches and controls to allow passengers in the vehicle to turn on individual lights are incorporated within most courtesy light systems. The system shown has individual two-position switches that allow the passenger to turn on a light. When the switch is pressed, it completes the circuit to ground for that light only.

Instrument Cluster and Panel Lights

Consider the following three types of lighting circuits within the instrument cluster:

  1. Warning lights alert the driver to potentially dangerous conditions such as brake failure or low oil pressure.
  2. Indicator lights include turn signal indicators.
  3. Illumination lights provide indirect lighting to illuminate the instrument gauges, speedometer, heater controls, clock, ashtray, radio, and other controls.

A rheostat controls the brightness of the instrument panel lights

FIGURE. A rheostat controls the brightness of the instrument panel lights.

The power source for the instrument panel lights is provided through the headlight switch. The contacts are closed when the headlight switch is located in the PARK or HEADLIGHT position. The current must flow through a variable resistor (rheostat) that is either a part of the headlight switch or a separate dial on the dash. The resistance of the rheostat is varied by turning the knob. By varying the resistance, changes in the current flow to the lamps control the brightness of the lights.

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