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2007 Chevrolet Silverado 2500HD - lights dimming or flickering

Dash lights dimming, overhead light flickering, headlights on and off while driving at night.
Switches? Fuse panel? Alt? Wiring harness?

Possibly a bad ground.

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Always assume a bad ground. Take alook at the voltmeter in the dash when this is happening. If the car reads less than 13 volts, you may have an alternator problem.

Even though it may not have anything to do with your issues I suggest you clean the battery connections. Just because they are so often neglected. Except for the dome light, the other issues seem to be related to the lighting circuit. The fuses for the headlights are most likely in the panel under the hood. Check the voltage on those fuses. If the voltage is okay there then the problem is most likely between the fuses and the relay for the lights. The trouble could be due to a faulty ground but if nothing else is having a problem then I tend to think that the problem is on the HOT side of the circuit. Knowing how the dome light is tied into the power along with the lighting circuit would help clue you in more to the location of the problem.

The BCM may be failing.

Tester