04Silverado, I checked those 3 wires (A7 and A6) and they were only supplying a few millivolts. How do I trace back A7 to find out why this wire is not getting the proper voltage?

I also took off the back panel on the gauge cluster and took one of the light bulbs out. I checked the voltage there and it was the same voltage as across A7 and A6 so those are the right wires. With the headlights off the voltage was only 20 millivolts and with the lights on around 8 mv which is basically nothing. I pulled out all the bulbs and checked to make sure they all worked and they do.

Does anyone know why I wouldnt be getting the proper voltage to the cluster back lights? Its only the large illuminating lights in the cluster. All the small ones for turn signals, high beams and such work fine. I just hate not being able to see what speed I'm driving at night.

 

On pin A7 you should see 12 volts with the dimmer at maximum brightness, A6 is the ground for the cluster backlighting. Did you check the ground and power separately? I would check them seperately so you know what direction to go in next. I did not ask this before, but does the backlighting for your radio and HVAC controls works? I can get you the wiring schematics if needed.

The reason the lighting for the turn signals and high beams work is because it is on another circuit, they are powered by ignition voltage to the cluster and grounded by the cluster ground. They are not tied into the backlighting wiring.

 

I remember checking A7 to A6 as well as checking A7 to metal and the readings were both the same. Radio is aftermarket so not sure if that applies but it does light up. I'm away at college and truck is at home, Ill ask my brother to check tomorrow if the AC controls lights up. You're just talking about the backlighting behind the ***** right?

 

For the HVAC backlighting I am talking about the *****, numbers for blower speed, colors for temperature selector and icons for vent position. If the backlighting for the HVAC controls does not work the problem is most likely the dimmer switch is bad.

 

My brother checked and said that the hvac back lights dont work so I ordered a new dimmer switch, hopefully that will be the simple fix for the problem. Thanks for your help 04silverado.

 

No problem, that is what the forum is for.

 

Well... the new driving lights/dimmer switch didnt fix the problem. The cluster backlights are still dead as well as the HVAC lighting. Any ideas on what to try next?

 

Check the illum fuse (#14 in the instrument panel fuse block). If the fuse is good then with a test light connected to ground check for power at the illum fuse with key on, lights on and the dimmer at full brightness. The test light should light. Let me know what you find.

 

Funny you mention the illum fuse. So i just got done trying to chase down why I wasnt getting the 12 volts to the two pins on the cluster for the past few hours. I found using the multimeter that I'm not getting any voltage to the illum fuse (actually a measly 30 millivolts). I traced that fuse, and there's a green wire that runs directly to the back of the dimmer switch. So what I did was I jumped a 12 volt hot lead to that green wire at the back of the dimmer and voila the backlights lit up as well as all the other lights in the HVAC and dash. Well it blew the 10 amp illum fuse the first time so I threw a 20 amp in there and it worked for some reason.

Any idea why I'm not getting the proper voltage across the illum fuse? Shouldnt I be getting 12 volts there? I was trying to track where the illum fuse gets power from?

Even though I cant dim the lights im stoked that it works at full brightness.

 

The illum fuse gets power from the dimmer switch which get power from the park lamp fuse. So the next thing to check is to see if your park lamps work.

The illum fuse will only receive voltage with the park lamps or headlamps on either using the switch or auto function. As you found the illum fuse is after the dimmer switch not before it.