2017 Yukon - Blinking headlights, but alternator and 2 batteries working fine

[Halas Empire]

 

[Halas Empire]

View attachment 439359

 

[Halas Empire]

I thought this was all linked to the stereo addition, but my headlights dim when I just press the power window buttons. Everything is happening after i slept the night and Yukon been idle for 12+ hours.

Just a weird problem, when the volt readout is 14.8 and I see the headlights dim

 

[Halas Empire]

Well... I had the Mechman 400 amp alternator installed and during the daytime I saw a difference, radio up, and ac on full and volt meter didn't budge. But at night, after a cold start after I've been home for 8 hours, headlights still blinking and even dimming when I press the windows buttons. I wanted the high powered Alternator anyway, but it seems like it's in the wires or next I will try getting a capacitor, which was suggested in a early reply.

 

[Halas Empire]

I'm going to try getting two new batteries first. I recently added a second battery, but keep the Everlast battery that came with the yukon, car unstaller said it was working fine, and headlights didn't start to blink until 3 weeks after install. So two identical batteries with the new alternator may fix it.

 

[Halas Empire]

The best battery I can find online seems to be Diehard Platinum AGM, then next step up is the Optima batteries

 

[Halas Empire]

I guess my problem has been solved, after installing two new batteries at the same time, instead of adding a second battery to the original, it had fixed the dimming lights. I wanted all the other stuff anyway, the 400 amp alternator and 2 batteries, just to max out the vehicle for a sound system. In the end, it was the most simplest thing. Also, when I had the two new batteries installed, I went with Optima yellow top, the audio installers had a good laugh at the cheap 10 gauge wire the GMC dealer used to install the alternator, they told me it could have made the alternator burn out, they replaced it for me. Thanks for all the comments.