Intermittent electrical problem 2nd Gen 4runner Need Help

I have been having this on and off issue with what I assume is something electrical. It was really bad in the winter and went away once it warmed up but now is giving me constant trouble again.

Just running everyday things will cause my power to cut out when I'm driving. A mix of using AC Radio and turn signal when I'm steping on the break to come to a stop will cause the battery gauge to drop to at least half even sometimes it has been known to cut off on me.

I replaced the alternator early this past December but I think that might be the problem. When I step on the gas everything goes back to normal. Even parked and rolling the windows up and down with the ac ca cause the same thing.

 

This is a little out there of an answer but you might be causing too much drag on the engine between the power consumption, brake application, and A/C. I remember one time I did stall the engine but tapping the brake too much. This is caused by the brakes using a vacuum line to give power to your brake system. That combined with the A/C compressor putting a lot of strain could be the cause, though this is unlikely as the engine should be able to handle a lot more going on but you never know. Try replicating the results but without the A/C on

One thing I would try also is take the alternator to a shop to get it tested before attempting to replace it again. It is possible that you got a dead one out of the box but a test will be able to tell you that without having to throw money away. Not sure if they all do it but I know my local napa will test alternators for free.