Mazda Repair: 94 Mazda B2300--electrical?, battery gauge, mazda b2300

Question
Hello,

I have a 94 Mazda B2300 pickup that has developed a strange issue as of late.  Several weeks ago, I went to start the truck, and it acted as if the 2 year old battery was dead.  A few minutes later, I tried it again and it started right up.  Several weeks went by, and after driving it for 25 miles, and shutting off the engine for 30 minutes, it again did the same thing.  I jumped it off with my wife's car and it started up and the engine ran fine.  However, whenever I would touch the brake pedal to put it in gear or turn on the headlights, it would come very close to dying.  Also, the Amp/Battery gauge would jerk constantly.  I suspected maybe the battery was bad and took it to have it tested.  The guy said the battery was bad, and I replaced it.  That was 3 days ago.  Today the truck started just fine, but the minute I stepped on the brake pedal or switched on the headlights, it would almost stalled, and the amp/battery gauge was jumping again.  I shut off the engine and then restarted it.  It started fine, and no sign of the stalling issue.  This is very unpredictable, and I'm afraid to take it out.  Any ideas as to what could be causing this?

Thank you,
John

Answer
i would start by checking all your ground wires i had a mazda 626 do the same thing and it turned out to be a bad ground wire, if your battery and alternator are good that would be the best first step. follow all the black ground wires check for any breaks corrosion or loseness and fix as you find the dont just stop when you fine one check them all to make sure.