Alternator?

[TechBoyJK]

Was given a 2006 Trailblazer with 55,000 miles. Runs great, but I noticed the lights/electronics seem touchy. The lights flicker a little bit over bumps, and when I try using any of the electronics, the lights dim pretty noticeably.

http://www.youtube.com/watch?v=ZduRnF5NnYc

Time for a new alternator? In the video I'm simply raising and lowering the drivers side window.

 

[SpatiallyAware]

What's the date on the battery? With that low mileage I'm guessing it wasn't driven often, which can be tough on a battery.

Also disconnect and clean the terminals.

To directly answer your question, it's unlikely to be the alternator.

It's either the battery, the battery connections, or a bad ground.

 

[DaTT]

Try the same thing with just battery power. ie. without the car running. Are the effects the same?

 

[LTC8K6]

If you have an auto zone or advance auto, they will check your charging system and battery for free.

You could just measure the voltage yourself to get an idea.

 

[Zenmervolt]

The first thing I'd do is check the main ground points. From that video it looks as though you're in an area that gets snow and probably road salt so I wouldn't be terribly surprised to find that the ground connections had corroded, which will greatly increase resistance in the circuit.

ZV