1998 Other Jeep Models V8 All Wheel Drive Automatic 123000 miles
Within the past week when driving with my lights on I have noticed that my 1998 Jeep Grand Cherokee Limited has had a dimmed dashboard. When the lights aren't on the control panel, CD player and mileage are illuminated normally. The dimmer switch is not making a difference when the lights are on and as far as I have seen there are no problems with my headlights, flashers, taillights, etc. Any ideas what the cause may be?
I have provided the operation of the lighting system. Assuming the dimmer switch is okay, and I say that because this should also control the other dash items. I would first check the bulbs in the cluster to see if they are burnt out. I have provided that.
Cluster Illumination Lamp
When the park or head lamps are on, the cluster illumination lamps light. Illumination brightness is adjusted by sliding the panel dimmer switch knob (downwards to dim, upwards to brighten). Each of the instrument cluster illumination lamps receives pulse-width modulated battery feed from the Body Control Module (BCM) on the hard-wired panel lamps driver circuit. The BCM monitors the panel dimmer resistor switch to determine the desired dimming level, then adjusts the pulse-width signal accordingly
The BCM also sends the proper panel lamps dimming level message on the Chrysler Collision Detection (CCD) data bus to control the dimming levels of the various vacuum fluorescent displays. All modules on the CCD data bus with vacuum fluorescent displays (instrument cluster, radio, mini trip computer, vehicle information center) receive this message and adjust their dimming levels to match that of the incandescent cluster illumination bulbs driven directly by the BCM.
Vehicles equipped with the automatic headlamps option have an automatic funeral mode or parade mode. In this mode, the BCM uses an input from the automatic headlamp light sensor to determine the ambient light levels. If the BCM decides that the exterior lighting is turned on in the daylight, it overrides the selected panel dimmer switch signal by sending a message on the CCD bus to illuminate all vacuum fluorescent displays at full brightness for easier visibility in daytime light levels. The automatic funeral mode or parade mode has no effect on the incandescent bulb dimming levels.
Each of the cluster illumination lamps is located on the instrument cluster circuit board. Each lamp has a replaceable bulb and bulb holder.
WARNING: ON VEHICLES EQUIPPED WITH AIR-BAGS, REFER TO AIRBAG SYSTEMS BEFORE ATTEMPTING ANY STEERING WHEEL, STEERING COLUMN, OR INSTRUMENT PANEL COMPONENT DIAGNOSIS OR SERVICE. FAILURE TO TAKE THE PROPER PRECAUTIONS COULD RESULT IN ACCIDENTAL AIR-BAG DEPLOYMENT AND POSSIBLE PERSONAL INJURY .
Remove the instrument cluster from the instrument panel. See Instrument Cluster for the procedures.
Remove the bulb and bulb holder from the circuit board on the rear of the cluster housing by turning the holder counterclockwise. CAUTION: Always use the correct bulb size and type for replacement. An incorrect bulb size or type may overheat and cause damage to the instrument cluster printed circuit and/or the gauges.
Reverse the removal procedures to install.
October, 23, 2008 AT 3:17 PM
One other note. If possible, since I don't show how the cluster is plugged in to the dash, once it is disconnected, and you can see the back where the bulbs are, I would turn the lights on and see if you can see which lights are burnt out. Another suggestion if you can not tell if the bulb is burnt out once removed, I have taken an ohm meter and did continuity check to verify that way. If you do find a few are burnt out, my suggestion is to replace them all. Might save time in the future on removing it again to replace the ones you didn't this time. It just seems that the bulbs would be the first thing to check and would go to cause the lights to dim.