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Discussion Starter · #1 ·
my right turn/brake signal doesn’t work. I replaced the bulb and still nothing. My interior lights do not work as well. The visor lights on both passenger/drivers side do not work. And the last light issue is the 2 control knobs for the headlights and transfer case back lights do not work. Checked all fusing(under hood, inside driver and passenger sides) and everything is good. My alternator isn’t overcharging. I am getting an output voltage of 14.3VDC. Any ideas? Thinking possible grounding issue? Not sure
 

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Do you have a 7 pin trailer plug? Check the connections in the plug and any splitters from rear lights to trailer harness. Could be corroded. As well as the ground at the back of the truck.
 

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From what you are describing go back to fuse panel again because you stated: "My interior lights do not work as well. The visor lights on both passenger/drivers side do not work. And the last light issue is the 2 control knobs for the headlights and transfer case back lights do not work."

You have 3 separate circuit issues


Has somebody poked around in this truck since new, especially in the interior cabin??? Installed aftermarket electrical crap???
Been in a vehicle accident???

Did you check "both sides" of "all" the fuses with these 3 separate circuits, key in off position???

Those knobs and taillight are on a separate circuits along with the interior lights.

Does the right "front" turn signal flash???

Is the interior light switch turned off by the dimmer control???

Here is a copy of the service manual link from https://www.gmupfitter.com/

http://www.gmupfitter.com/files/media/photo/578/Sierra_Silverado_Electrical_Body_Builders_Manual_Service_Manual_2015_en_US.pdf

You have a lot of studying / work to do.

Will be in the background once you look at each circuit.

Don't worry about the alternator it's working normal.
 

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You could be experiencing a corrosion problem in the underhood fuse panel.
The '07 to '14 trucks had the problem, a number of my friends have had their panels changed.
When the dealer stocks each of the 3 panels used by those trucks, you know its a common problem.
But the '15 may not suffer from this problem, this is only a suggestion.
 

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The previous fuse panels were mounted so the wheel splash would hit them on the bottom side. I suspect no splash shield.
Water, salt and electric current makes for quick corrosion.
 
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