No Gauge Cluster Lights

[kelracing33]

I have searched the forums both here and another forum all to come up empty. I have an 04 Z71 tahoe with no gauge backlights, all the informational lights work such as the ce lights and all the blinkers and what not, as well as all gauges work. I pulled one light and checked it with a 12v powersource and it lights right up. I have power at the a11 plug wire that is labeled to be power to gauge illumination. I checked the resistors to the left of the speed stepper motor and all looked and felt to be solid. Any other source that could be the problem? One post said the bcm, but im not having illumination issues across the board as he indicated, just the cluster, not the hvac, steering wheel controls or any other backlights. Any help would be appreciated.

 

[Rocket Man]

Possible ground problem? We always seem to forget power doesn't work without a ground. Also could be your dimmer switch; there should be a positive voltage that increases and decreases when you turn your dimmer up and down. Edit: I see your other backlights work so probably not the dimmer.

 

[kelracing33]

Possible ground problem? We always seem to forget power doesn't work without a ground. Also could be your dimmer switch; there should be a positive voltage that increases and decreases when you turn your dimmer up and down. Edit: I see your other backlights work so probably not the dimmer.

I watched a video by ClusterFixWashington I believe that was referring to a similar issue being caused by poor connection at the plug on each individual pin inside the plug getting fatigued over time. Followed his guidance on pulling appropriate pins and giving them back a little tension around the corresponding pin inside the cluster. Tried it again after that and still no lights, the only way I could quickly think to check the dimmer switch, was throwing a test light on the pins and checked all power sources and ground pins in that plug and all worked as they should. I am going to recheck all tonight. I tested those resistors by plugging in the gauge board without the overlay and pressing on them individually with a pencil eraser ( non conductive ) to test connections. I'm kinda at a loss at this point

 

[Rocket Man]

Sounds like you need an inexpensive multimeter to trace the circuit board looking for a broken joint. Probably need to figure out which pin is the dimmer circuit in the wiring harness(the one where your test light dims and brightens when you adjust the dimmer) and then locate that pin on the circuit board, then use the meter with the continuity function enabled and test that circuit on the board from where it connects to the pin to where it goes to the first light, looking for a broken trace or solder joint. Also the same for the ground circuit on the lights.

 

[kelracing33]

I've misplaced mine in our recent move, gonna grab a cheap one Wednesday and trace it. Luckily 8 years as a generator mechanic is the Army prepared me for it. Looking up wiring diagrams is like asking for pics of Area 51 any idea where to access a wiring diagram or schematic? Thanks again for your help!

 

[Rocket Man]

PM sent. If you give me your email I have a .pdf service manual and it has 2003 Suburban wiring diagrams. Should be the same as 2004 Tahoe. I checked and it has the instrument cluster; I see the illumination circuit on it. I can send what I have which isn't a complete manual but it should work for you.

 

[kelracing33]

PM sent. If you give me your email I have a .pdf service manual and it has 2003 Suburban wiring diagrams. Should be the same as 2004 Tahoe. I checked and it has the instrument cluster; I see the illumination circuit on it. I can send what I have which isn't a complete manual but it should work for you.

Welp, figured it out, the bulb I pulled out to check and worked, must have had a cold solder or wasn't fully connected. Anyways, every dang bulb other than that one was blown. So, after checking the dimmer switch, checking all the pins in the plug, checking continuity between every component in the illumination system, its the friggin' bulbs. Needless to say all will be fixed on Saturday.

 

[Rocket Man]

Awesome, congrats!

 

[kelracing33]

Thanks again for sending that manual, really helped track down everything in the system. Also as a side note, I pulled my driver temp, and mode door actuators for a cleaning (intermittent hot air issue on driver side, like everyone else, also didn't have defrost) used your recalibration technique and now everything works as it should. +1 for Red Rocket

 

[Rocket Man]

Sweet; glad to help.