Digital odometer/trip meter works, but not illuminated.

Odometer
The odometer is an electronic digital display. Digits displayed are illuminated by the odometer backlight bulb. The odometer backlight bulb brightness is controlled by class 2 messages from the BCM to adjust the display for daylight and instrument panel dimming operation. The trip odometer and total odometer will show in this display area. The push button in the lower right side of the speedometer is used to toggle between the trip and total odometer readings. To reset the trip odometer, push and hold the button down for at least two seconds. The total odometer display has six digits with no decimal display. The trip odometer has four digits including a decimal point and indicates tenths of a mile or kilometer.
The body control module (BCM) stores the vehicle mileage. If the BCM fails, the cluster will display the last valid mileage that was sent before the BCM failed. For replacement of the BCM refer to the BCM section of this service manual. Replacement instrument clusters do not require odometer pre-setting before installation. If the instrument cluster is replaced, the mileage stored in the BCM will be sent to the new cluster via serial data, and shown in the odometer display.

Your best bet , take it to a qualified repair shop.

You can try doing a re-calibration of the cluster. To do that.....
Begin the test with the ignition switch in the OFF position. 2. Depress the odometer/trip odometer switch button. 3. While still holding the odometer/trip odometer switch button depressed, turn the ignition switch to the ON position, but do not start the engine. 4. Release the odometer/trip odometer switch button. 5. The instrument cluster will simultaneously begin to illuminate all of the operational segments in the VFD units, and perform a bulb check of each operational LED indicator. The VFD segments and LED indicators remain illuminated as each gauge needle is swept to several calibration points and back. If a VFD segment or an LED indicator fails to illuminate, or if a gauge needle fails to sweep through the calibration points and back during this test, the instrument cluster must be replaced. 6. The actuator test is now completed. The instrument cluster will automatically exit the self-diagnostic mode and return to normal operation at the completion of the test.

Could be a fuse. Have somebody who knows about cars look at the instrument cluster fuse to see if the wire inside is broken.

a fuse blew.
this car has an electronic dash cluster. (with brain)
first is fuses. (check them first) (2 of them)
second is scan it. scan the PCM for DTC error !

if rpm dies, for sensors the engine dies...
The PCM runs spark and injection off 2 sensor and RPM
if they die so does spark and injection.
the cluster has self test mode, try that first?
this proves the cluster is ok.
this is covered in the FSM for your JEEP

the WJ jeep
Chapter 8J covers all this.. to great details.
page 8
fuse 17 and 22 must be good. JB box, cab.

posted now 100 of times, here it is again.
quote
The instrument cluster actuator test will put the
instrument cluster into its self-diagnostic mode. In
this mode the instrument cluster can perform a selfdiagnostic
test that will confirm that the instrument
cluster circuitry, the gauges, the PCI data bus message
controlled indicators, and the electro-luminescent
illumination lamp (if equipped) are capable of
operating as designed. During the actuator test the
instrument cluster circuitry will sweep each of the
gauge needles across the gauge faces, illuminate each
of the segments in the Vacuum-Fluorescent Display
(VFD), turn all of the PCI data bus message-controlled
indicators on and off again, and turn the electro-
luminescent illumination lamp (if equipped) on
and off again.
Successful completion of the actuator test will confirm
that the instrument cluster is operational. However,
there may still be a problem with the PCI data
bus, the Powertrain Control Module, the Airbag Control
Module (ACM), the Body Control Module (BCM),
the Controller Anti-lock Brake (CAB), the Sentry Key
Immobilizer Module (SKIM), or the inputs to one of
these electronic control modules. Use a DRBIIIt scan
tool to diagnose these components. Refer to the
appropriate diagnostic information.
If an individual indicator lamp or the electro-luminescent
illumination lamp do not illuminate during
the actuator test, the instrument cluster should be
removed. However, check that the incandescent lamp
bulb is not faulty, that the bulb holder is properly
installed on the instrument cluster electronic circuit
board, or that the electro-luminescent lamp pigtail
wire connector is properly connected to the instrument
cluster electronic circuit board before considering
instrument cluster replacement. If the bulb and
bulb holder, or the electro-luminescent lamp connection
check OK, replace the faulty instrument cluster
unit.
(1) Begin the test with the ignition switch in the
Off position.
(2) Depress the odometer/trip odometer switch button.
(3) While still holding the odometer/trip odometer
switch button depressed, turn the ignition switch to
the On position, but do not start the engine.
(4) Release the odometer/trip odometer switch button.
(5) The instrument cluster will automatically
begin the actuator test sequence, as follows:
(a) The cluster will turn on, then off again each
of the PCI data bus message controlled indicators
(except Airbag) to confirm the functionality of the
indicator and the cluster control circuitry:
(b) The cluster will sweep the needles for each of
the gauges from minimum to maximum and back
to minimum to confirm the functionality of the
gauge and the cluster control circuitry:
(c) Only on models with a premium version of
the cluster, the cluster will illuminate the electroluminescent
lamp and turn it off again to confirm
the functionality of the lamp and the cluster control
circuitry.
(d) The cluster will sequentially step the odometer/
trip odometer VFD display from all zeros
(000000) through all nines (999999) to confirm the
functionality of all VFD segments and their control
circuitry, then display the software version number,
followed by "DONE".
(6) The actuator test is now completed. The instrument
cluster will automatically exit the self-diagnostic
mode and return to normal operation at the
completion of the test, if the ignition switch is turned
to the Off position during the test, or if a vehicle
speed message indicating that the vehicle is moving
is received from the PCM over the PCI data bus during
the test.
(7) Go back to Step 1 to repeat the test, if
required
end quote.


if this passes and fuses are good
then you may have DTC errors scanned
if you scan it and you see comminications error from PCM to cluster, well that be it. ... and am not going into THAT>here.

see this causes and fix it. God bless you
measure test voltage at the last common circuit point. If voltage is NOT present a this point work toward the battry to find the fault

First thing to check is the interior light / dome light control. It is usually located to the left of your instrument panel (where your odometer is located). It you move this dial up or down it will control the intensity of interior lighting.

However, if that does not cure the issue, it is possible that you have a short somewhere, or a bad bulb for the instrument panel. At that point, I'd take it to your local repair facility and have them check it out. Changing interior lighting or testing for electrical failures can be a difficult task.

Section 13-01: Instrument Cluster—Conventional 1995 Thunderbird, Cougar Workshop Manual REMOVAL AND INSTALLATION Instrument Cluster Removal and Installation

1. Disconnect battery ground cable (14301) .

1. Remove screws holding instrument panel reinforcement (017A28) .

1. Remove screws holding instrument panel lower shield (045G02) .

1. Remove fasteners holding steering wheel column as outlined in Section 11-04 . Gently lower steering column.

1. Remove fasteners holding the instrument panel finish panel (044D70) and gently pry off.
   
   
   
   

1. Remove four instrument cluster retaining screws. (Do not remove screws from the instrument cluster main lens (10887) and instrument cluster mask (10890) ).

1. Slide the instrument cluster (10849) to the right of the instrument panel opening and unhook the instrument panel harness from the back of the instrument cluster .

1. Remove the instrument cluster from the instrument panel (04320) .

-----------------------
Speedometer/Odometer Federal law requires that the odometer in any replacement speedometer (17255) must register the same mileage as that registered in the removed speedometer . Since the speedometer mileage cannot be reset on this unit, affix odometer sticker to driver's door pillar and record original vehicle mileage. Removal

1. Disconnect battery ground cable (14301) .

1. Remove the instrument cluster (10849) as outlined.

1. Remove seven screws retaining the instrument cluster mask (10890) and instrument cluster main lens (10887) .

1. Remove speedometer assembly.

Installation

1. Position the speedometer assembly to the instrument cluster back plate (10848) and install.

1. Position the instrument cluster mask and instrument cluster main lens to the instrument cluster back plate and install the seven retaining screws.

1. Install the instrument cluster as outlined.

1. Connect battery ground cable and check the operation of the speedometer .

please rate if this helps

it sounds like you are getting a surge of voltage from your alternator/generator. Very strange.

the dealer can run a diagnostic test & pull fault codes or you can try this. If this helps, please report back & rate as fixya. Thanks. I am curious what you find as root cause. Good luck.

Instrument Cluster Self-Diagnostic Mode
To enter the instrument cluster self diagnostic mode with the engine off, depress and hold the odometer reset button. Turn the ignition switch to the RUN position and hold until the gauges sweep (within five to eight seconds). Depress the reset button once to advance to each stage of the self-test.
Turn the ignition to the OFF position to exit the instrument cluster self-diagnostic mode. If no DTCs related to the concern are retrieved, proceed to the Symptom Chart to continue diagnostics.


Instrument Cluster Self-Diagnostic Mode Odometer display Description GAGE Carries out gauge sweep of all gauges, then displays the present gauge values. Also carries out the check sum test on ROM and EEPROM. All segments illuminated. Illuminates all odometer segments. bulb Illuminates all micro-controlled lamps and LEDs. r #### Returns to normal operation of all micro-controlled lamps and LEDs and displays hexadecimal value for ROM level (used when requesting assistance from the hotline). nr#### Displays hexidecimal ROM level and type as stored in non-volatile memory (NVM). EE ## Displays hexadecimal value for EE level (used when requesting assistance from the hotline). dt #### Displays hexadecimal code for the final manufacturing date. ###C Gas engines display last temperature gauge input value from SCP, temperature gauge will indicate present temperature. Diesel engine displays present temperature analog/digital input in decimal as a ratio, temperature gauge will indicate present temperature. dtc #### Displays a 16 bit DTC in hexidecimal format. DTCs displayed are those detected in continuous operation not during self-test. EnG Displays English speed value being input, speedometer will indicate present speed. m Displays metric speed value being input, speedometer will indicate present speed. tAc Displays the tachometer value being input to the instrument cluster. Tachometer will indicate present rpm. FUEL Displays the present analog/digital fuel level being input to the instrument cluster as a ratio. OIL Displays the last analog/digital reading of the oil pressure switch contact resistance, oil gauge will indicate present level. br Displays the brake fluid level in an analog/digital ratio value. bAt ##.# Displays present battery analog/digital voltage. rhEo Displays present hexadecimal pulse width modulation (PWM) dimming input. rhi, rhS, rho Alternating 1 second display of pulse width modulation (PWM) input duty cycle, SCP hexidecimal dimming step, output driver counts in hexadecimal. Cr RUN/START sense circuit check. PA, Pb, PC, and Pd Displays 8-bit hexadecimal value for the Port A, B, C, and D readings (used when requesting information from the hotline). PE0-PE7 Displays 8-bit hexadecimal value for the Port E0-Port E7 in analog/digital readings

it's most likely the cluster if one function works and the other doesn't. And, you likely have an electronic vehicle speed sensor that sends a signal to your analog cluster that then dispays your speed and odometer.

It may be possible to get instrument cluster to do a self-test? If you want to try this to rule out instrument cluster.
Press and hold odometer reset button, turn key from off to run, run is where the dash lites come on. Any stored 3-digit codes will be displayed in the odometer vf display. The vf display will perform a sequential segment test. All indicators, data controlled, will illuminate. All gauges will cycle in 12.5% or 15% increments. The cluster will automatically exit self-test. The self test does not verify serial data stream. The cluster internally commands all non-hardwired gauges and indicators to operate. The fuel level sending unit sends info to pcm then pcm sends data to instrument cluster.
I don't know if that self-test will work on your vehicle? It won't hurt to try. If all the gages cycle except fuel gage, then I suspect the instrument cluster. You can call around different shops, get an estimate for the repair.