battery/electrical issues

problem/symtoms: battery tests good by autozone and is only about 4 months old, and ive check it myself with a multi meter, 12.5v. new altenator bout a month old. car feels like a dieing battery, like lights dim when i try to start or sometimes no power at all. assecorys have weak power too, without starting car, like in the on postion. checked terminals for corrosion,and all fuses ok. the kicker is sometimes itll start up no problem. turn it off, start up again fine. i though i fixed it cuz the positive cable was slightly loose. tightened, started fine a couple more time, didnt go anywhere went to bed woke up and problem still persists. only thing i can think of is ground, short, or maybe a relay. i hate electical nor am i that good with it. any help/direction would be appriciated. thanks

check the grounds or replace the connectors on the battery

got it fixed yesterday. it was the terminals. was only pushing round 8-9volts. i never heard of them losing conductivity with no corrosion. but thanks tweety2300. it only took over 50 views for someone to respond.

The stock terminals on thses cars are junk anyway I had the same problem that's why I knew