Dimming lights/lights go out

I've got a 2008 regular cab tacoma 4x4. 2.7 of course, 5 speed

Recently I've been having some funky symptoms. Driving at night, there is noticeable dimming of the lights, especially when turning on something else electrical. Even hitting the brakes or turn signal will create a noticeable dimming before bouncing back to normal. Occasionally when taking off from a stop, ALL of the lights etc go off for a moment. Ie dash lights, radio, etc. Then come back on, almost as if I just restarted the truck.

The battery is a 8 month old Optima red top and tests good. I checked voltage after sitting overnight at 12.7 volts. Running when truck is cold is around 13.8. After warming up it is around 13.2, and Occasionally dips to around 12.6 or so. Voltage at 2k remains is around 13.2 as well.

Question is, could this be a bad voltage regulator or possibly an alternator on it's way outrank? Truck is all stock, 91k miles.

 

My vote would be alternator about to go out as you suggested or possibly a poor electrical connection??

 

Get the alternator load tested for a start, most parts stores do it free.