Instrument Cluster Lights Not Working

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6 years 8 months ago #54768 by ZachSyndy
Instrument Cluster Lights Not Working was created by ZachSyndy
I have a 1999 Chevy Silverado 1500. And the back lights to the Tachometer, Speedometer, gas, oil, battery, and Temp Gauges do not work, as well as the back light to my climate Control. The Gauges themselves work fine as well as the Climate Control but the Lights don't. I have Replaced the Dimmer Switch/ Headlights Switch, the entire Cluster itself, Checked and rechecked the fuzes and bulbs, and the DLR (Day Light Running Lights) Sensor and everything seems fine. I bought the truck with the dash lights already out and not working, he did install a aftermarket stereo. I have looked behind to see if there are any grounds or bare wire and it seems ok (i haven't done a full detail check, but i have taken the stereo out and looked around). I have a Video on youtube showing you if you need some visual
. Any ideas????

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6 years 8 months ago #54789 by Monte
Replied by Monte on topic Instrument Cluster Lights Not Working
Have you worked through the wiring diagram on this? Sounds like a bad connection somewhere along the way.

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6 years 8 months ago - 6 years 8 months ago #54790 by Wrench Turner
Replied by Wrench Turner on topic Instrument Cluster Lights Not Working
Here are three TSB's that might address ye' problem:








Here is a copy of the ground distribution of your interior driver amenities. Although there are a lot of devices tied into a common ground, there does not appear to be a correlation between the radio and the instrument panel cluster:



Here is the power distribution to the instrument panel cluster. It appears that the IPC gets power from circuit #1020 via a pink .35 gauge wire spliced from the 'TRANS' (fuse #20) 10amp fuse, delivered through 'pin #7' via a female connector to the IPC:


"Do not catch yourself on fire."
Last edit: 6 years 8 months ago by Wrench Turner.

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6 years 8 months ago - 6 years 8 months ago #54796 by ZachSyndy
Replied by ZachSyndy on topic Instrument Cluster Lights Not Working
Is it the wiring ignition switch/starter or just the Ignition Key Switch/Lock?
Last edit: 6 years 8 months ago by ZachSyndy.

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6 years 8 months ago - 6 years 8 months ago #54798 by Wrench Turner
Replied by Wrench Turner on topic Instrument Cluster Lights Not Working

Is it the wiring ignition switch/starter or just the Ignition Key Switch/Lock?


I don't know. I need more information. Basic electrical testing needs to be performed.

Based on the TSB's recommendations as well as my own knowledge of basic electrical theroy, I have devised a general strategy to help remedy your problem with the IPC and HVAC temperature control head:
  • Remove the 2 aforementioned devices from the dash
  • Disconnect the electrical connections
  • Test for power to the devices
If power:
  • repair or replace failed device(s)
If no power:
  • check battery voltage
  • verify fuse continuity
  • turn ignition key to ACC
  • disconnect and reconnect all associated wiring harnesses (as per TSB)
  • Perform 'wiggle test' on all wiring harnesses
  • visually inspect wiring for a possible open in the circuit. if an open cannot be detected, splice into known good circuit close to the fuse box and run a parallel line to the associated affected device(s)

[/ul]One more additional test
:
One thing that I wasn't sure if I wanted to include in the above list is to check the affected non-working devices by applying power directly to the affected circuits/devices from an outside source and see if they light up.

Final thoughts:
I like the TSB stating that it might just be an open in the ignition switch. I believe it would be worth your time to perform the testing on the ignition circuit as stated in the TSB. It is quite possible that you are only 1 ignition lock cylinder away from restoring your lights. :)

One thing that all your affected devices have in common is the dimmer rheostat. Perhaps it is possible that the dimmer is stuck in a 'off' or 'low' setting and has since been rendered unresponsive. I'm going to try to do some further study to see how it can be tested. I might have to utilize my school's resources though, so I might not respond until sometime tomorrow.

Q: Does the interior dimmer rheostat have an affect on any other interior lighting?

"Do not catch yourself on fire."
Last edit: 6 years 8 months ago by Wrench Turner.

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6 years 8 months ago #54803 by htwr
Replied by htwr on topic Instrument Cluster Lights Not Working
I assume that no dash lights are working, is that correct? if it is, also check to see if the tail lights are working. the tail lights and the dash lights are usually on the same circuits.if the tail ligths are working ok then you may want to start your testing with dash grounds. voltage drop testing can confirm their integrity. if all of the lights are inopertive including the tail lights , then you most likely have a power issue.
Keep posting and good luck.

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6 years 8 months ago - 6 years 8 months ago #54812 by Wrench Turner
Replied by Wrench Turner on topic Instrument Cluster Lights Not Working
Now that I have access to school resources, I now have a good schematic for the IPC:


IPC Description and Operation

INSTRUMENT CLUSTER
The standard instrument cluster contains a microprocessor. The instrument cluster micro processor communicates with other modules in the vehicle over the Class 2 serial data line. The information passed over the Class 2 serial data line, along with dedicated circuits to specific sensors and modules, provides the inputs which are used to operate all the gauges, indicators and the message center in the cluster. The instrument cluster continuously processes class 2 serial data in order to determine the correct values and states to display. When replacing instrument panel cluster assembly, federal law requires that the odometer reading of the replacement unit be set to register the same mileage as the prior odometer. If the same mileage cannot be set, the law requires that the replacement odometer be set at zero and a label be installed on the drivers door frame to show the previous odometer reading and the date of replacement.

The instrument cluster includes the following components:
  • Gauges Indicators
  • Message center
  • Tachometer
  • Speedometer/Odometers
  • PRNDL
Interior Lights

NON-DIMMABLE LAMPS
Voltage to the coil of the courtesy lamp relay, dome, reading lamp, courtesy lamps, cargo Lamp, Instrument Panel (IP) compartment lamp and the underhood lamp is supplied from the Inadvertent power relay on CKT 1732. The inadvertent power relay receives voltage from the CTSY LP fuse which is hot at all times. Ground for the courtesy lamps goes through the courtesy lamp relay. Both relays are controlled by the Body Control Module (BCM) based on inputs from door jamb switch, dome lamp switch or door handle switch. The BCM will supply a ground to the courtesy lamp relay when closing any one of the above switches to ground. Ground for the reading lamp, cargo lamp, IP compartment lamp and the underhood lamp is supplied by its own ground.

Voltage to the ash tray lamp and power window/door lock switches is supplied from the INT PRK fuse. Voltage to the INT PRK fuse is supplied from the park lamp relay, and is hot when park lamps or headlamps are on.

DIMMABLE LAMP
With the headlamp and panel dimmer switch in the park or head position, voltage is supplied to the IP dimmer switch via CKT 44. The voltage output of the IP dimmer is veritable and goes through the ILLUM fuse via CKT 8 to the cluster, radio and various IP switches. For the radio and cluster displays and some switches, an additional circuit is required, CKT 1382, for the these components to dim. CKT 1382 is a 12 volt output of the BCM, and is hot when park or headlamps are on.

Some circuits are monitored by the BCM, and upon failure may set a DTC.

Interior Lighting Schematic:


Dimmer Switch Schematic:

"Do not catch yourself on fire."
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Last edit: 6 years 8 months ago by Wrench Turner.

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6 years 8 months ago #54813 by ZachSyndy
Replied by ZachSyndy on topic Instrument Cluster Lights Not Working
The information/message lights will work on the dash (such as check engine lights/seat belt light etc. Just not the lights to the Volts,Fuel,Temp,Oil,Tachometer,and Speedometer. Also my Tail lights are working.

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6 years 8 months ago #54814 by ZachSyndy
Replied by ZachSyndy on topic Instrument Cluster Lights Not Working
@Wrench Turner, ill be sure try that. but how would i test to see if im even getting power to the IPC and climate control head?

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6 years 8 months ago - 6 years 8 months ago #54815 by Wrench Turner
Replied by Wrench Turner on topic Instrument Cluster Lights Not Working

ZachSyndy wrote: The information/message lights will work on the dash (such as check engine lights/seat belt light etc. Just not the lights to the Volts,Fuel,Temp,Oil,Tachometer,and Speedometer. Also my Tail lights are working.

General Information


The Instrument Cluster (IPC) indicators are illuminated by one of the following methods:


The IPC detects a concern with a discrete input.
A module sends a indicator illumination request message, via the class 2 serial data line.


Could be a problem in the communication bus... possible dead, babbling, or disruptive module.

"Do not catch yourself on fire."
Last edit: 6 years 8 months ago by Wrench Turner.

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