Ok..here's something thats been rattling my brain for months now. My 08 silverado has an electrical problem. I noticed it seemingly out of nowhere...I was driving slow down a road and was hitting the brakes often to keep my speed down and I noticed the slightest headlight dimming when I hit the brakes. So I stopped, put it in park and hit the brakes repeatedly...my headlights were dimming for sure. But, not only do the brake lights make it dim, but rolling up the windows, blinkers...any electrical load on the system causes the dim. And all of my lights dim when I load the system...headlights, interior lights, etc.
It's bad enough that my friend can communicate in morse code with the cars in front of us while we're driving just by pulling up on the window switch. Drives me insane.

This didn't happen after any mods...it seems like it just came out of nowhere. I've tried taking a wire brush to the grounds, replaced the alternator, even added a ground wire from battery to frame...no improvement. Electrical system checks out great on an Interstate battery/charging system tester.

So I'm clueless. Any ideas?

 

If it's still under warranty I'd just take it in.

 

fwiw most any gm ive ridden in does it a little bit when stopped/idle and use any extra electrical. My headlights dont do it because of the hids, but you can see the interior lights do it. I would agree you shouldnt be able to do morse code while driving down the road, should be charging fine then imo.. Dont the newer trucks come with the higher amp alt since they have efans??

You could take it to the dealer but i doubt there going to be able to help you any.. There is so much electrical stuff on new cars now adays that any draw pretty much puts load on the alt to keep up, thats why automotive companys are close to stepping up to 42volt systems.
You could try bigger Ga wire a little from the alt to battery, but i still doubt that will help. Or a pulley for the alt might help, i dunno..
Dont have and U/d pulley do you?

 

Funny you mention that...I did take it in and I showed them the dimming problem. After a couple hours of waiting they came back and said it was the amplifiers for my stereo in the truck. So I drove out of the dealership, removed the amp fuse, and drove right back in with it in my hand. They took it for a couple more hours only to tell me that my electrical system checks out good on their system, so they couldn't do anything. Pretty much a slap in the face to me.

 

No underdrive pulley either. And when I replaced the 145A alt, I put a 200A in its place...still no bueno.

 

Well that blows.
Have you tried a Big 3 mod yet?

 

I tried the ground from the battery to the frame... I kind of ruled out the rest of it because I didn't change anything about the electrical system. If there was a problem after installing my amplifier, I would have seen it after installation. But this popped up almost 2 years later. It still dims with the fuse pulled out, so... It's essentially back to a stock setup with that, so the problem is in the stock equipment for sure.

On the other hand, the dealership doesn't think theres a problem at all.........

 

Increase the AUG from the Alt to the battery at least.
Do you run your system heavy alot? Could have weakened the battery if so.

 

I thought about that, but the battery still checked out good on the tester. And it wasn't some walmart toy battery tester like the ones at autozone, it was one of the beast ones. So I trust its judgment.

 

Do you have a capacitor? they can do more harm then good sometimes.
and only thing i can think to do off the top of my head is the big 3 like mentioned and a overdrive pulley for the alt, but you already got a 200amp so i dont think that will help. the big 3 might help some but i also doubt it. Like i said any draw puts a sudden strain on the system and its got to kick the reg on and thats were your surge comes from..