Instrument cluster back light

[guapo79]

I know this has been discussed before but wanted to get any additional insights with my problem

My instrument panel works fine. Except no backlight, at any dim level. But the mileage does go bright when the lights are on and the mileage also dims with the mf switch.

Things I've tested:

Fuse 1 is fine. And all the lights it protects work.

Checked the ground under the driver speaker panel. It's fine.

Checked the illumination wire to the stereo, it's fine and the stereo also goes into night mode when lights are turned on.

Checked the resistance on the multi function switch, each setting on the dimmer shows proper ohm resistance.

Unplugged, cleaned and reseated both wiring harnesses behind the cluster

Tested a cluster bulb directly with 12v and it lights up fine

Anything else to test / check? Any other solutions?

Anyone know what pins I could connect on the cluster direct to 12v and ground maybe to test if I can get it to illuminate? It's a black 16 pin harness on the left and a white one on the right with an odd configuration.

 

[macleanflood]

Have you checked the resources section for the FSM for your year? Section 8w will have the wiring diagrams and pin outs for that connector.

-Mac

 

[guapo79]

Have you checked the resources section for the FSM for your year? Section 8w will have the wiring diagrams and pin outs for that connector.

-Mac

Found the FSM and downloaded it. Going to go through their continuity checks in the troubleshooting guide and see what I find.

 

[guapo79]

Found the FSM and downloaded it. Going to go through their continuity checks in the troubleshooting guide and see what I find.

So I'm stumped. Checked the continuity as described in the fsm between the various pins on both the cluster and mfs, and all checks are good. Applied voltage directly to the cluster pins for ground (c1 pin 5) and illumination lamps (c2 pin 6) and that lights all 5 bulbs up. Checked voltage on all the mfs fused pins, all good. Checked the mfs dimmer resistance and each dimmer setting is good.

The illumination signal is getting to the radio when the park lights are turned on, and the dimmer is even dimming the digital mileage on the cluster.

I don't have a drbiii tool to test the cluster with it, but I would think if the lights work with direct voltage, that the cluster is good.

Does anyone know where the c2 pin 6 power comes in from? Is it from the mfs or somewhere else? The FSM isn't clear to me on that. I think the mfs is fine, wondering if there's an issue with the voltage that comes into pin 6.

 

[B1Toad]

What about checking where the pins connect, in other words, run jumpers from the sockets to the corresponding socket pins to rule out a contact problem between the socket and cluster pins.

 

[guapo79]

I checked all the harnesses through jumpers, no issues there.

So I checked voltage on the cluster harness c2 to pins 6 and 15, neither one had voltage. 6 is the orange illumination wire and 15 is the red dimmer wire. Are either or both of these supposed to get voltage? I would think at least pin 6 orange would. If so, could I just run a new wire from somewhere?

 

[rasband]

I checked all the harnesses through jumpers, no issues there.

So I checked voltage on the cluster harness c2 to pins 6 and 15, neither one had voltage. 6 is the orange illumination wire and 15 is the red dimmer wire. Are either or both of these supposed to get voltage? I would think at least pin 6 orange would. If so, could I just run a new wire from somewhere?

View attachment 558393

Did you ever make progress on this? I have a similar issue and have landed at the same spot...

 

[guapo79]

Did you ever make progress on this? I have a similar issue and have landed at the same spot...

I never figured it out. I ended up wiring in new led bulbs into the instrument panel and putting them on a switch.

 

[rasband]

I never figured it out. I ended up wiring in new led bulbs into the instrument panel and putting them on a switch.

That's roughly where I've settled too, especially since I don't drive it much at night.

 

[JMT]

That's roughly where I've settled too, especially since I don't drive it much at night.

Could you swap someone else’s cluster in just to see if it’s something on the cluster side of the connections?

 

[jjvw]

That's roughly where I've settled too, especially since I don't drive it much at night.

Make sure the multifunction switch is fully plugged in

 

[jonny jeep]

In late model TJs with the dimmer on the multifuction switch, the dimmable lamps are contolled by a chip on the cluster circuit board. There can be an issue with the cluster circuit board where PCB tracks burn out stopping the cluster/dash lighting from working.

The fix is to either use jumper wires to bypass the burnt PCB tracks and restore the dimmable function, or link the black/yellow wire at C1 pin 4 to the orange wire at c2 pin 6. This will run the cluster/dash illunination at full brightness, but has been used as a workaround in the past, and may be easier than running link wires across the cluster PCB.