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