Instrument Panel Dimmer Switch Inspection

Remove the instrument panel dimmer switch. See INSTRUMENT PANEL DIMMER SWITCH .

Inspect for continuity between the dimmer switch terminals using an ohmmeter.

Fig 1: Inspecting Instrument Panel Dimmer Switch

Courtesy of MAZDA MOTORS CORP.

Inspection

INSTRUMENT PANEL DIMMER SWITCH INSPECTION REFERENCE

Circuit to test	Connect self-powered test light or ohmmeter to terminals	Move switch to these positions	A good switch will indicate
Interior lamps	1 and 3	On	Closed circuit
Interior lamps	1 and 3	Off	Open circuit
Illumination dimmer resistor	2 and 4	Rotate knob clockwise	Ohmmeter will show smoothly increasing resistance

Component testing procedure (voltage applied)

Disconnect the ohmmeter; connect pin 2 using a fused (10A) jumper to 12V DC power and pin 4 to ground.

Measure the voltage between pin 2 and pin 4 while rotating the thumbwheel from full illumination to no illumination. If the voltage smoothly decreases from near 12 volts to near 0 volts, the illumination dimmer is OK.

If not as specified, replace the instrument panel dimmer switch.