Why Is There Always Something Wrong?

first,was the car running???What is your battery voltage??If you were playing the stereo with the car ff for a while,the bass will kill the battery pretty quick,that why i run 2 batteries in whatever i have,even my Sea Doo.

give me more info

It sounds like your battery isnt charged enough. I had the same thing happen to me. My battery had a slow drain it it from having my autometer guages hooked into a fuse that wasn't ignition only. One day my car wouldn't turn over due to not having enough battery voltage. So I just sat in the car and listened to some music for a bit. Well the next time I went to listen to music if I turned the music up too loud it would shut off, then come back on. If I didn't turn it down it would keep doing this. Then I decided to turn the headlights on and it would shut the stereo off just like yours is doing. I didn't even think about the battery being the issue. I started tracing wires to try and find bad connections, grounds, etc. With no luck. I finally had the battery tested and the battery was toast due to being discharged so much. Put a new battery in and problem solved. Sounds like you may have drained yours a little too much, and with your amp and subs hooked up, they take too much juice from the system and they cut out. Try charging your battery, or drive around and charge it but leave your stereo turned off. See if that works. Or possibly it's time for a new battery?

Doesn't sound like a battery problem then if it's only 4 months old. Could be your alt. not holding up. What size is your alternator? I see you have a 90 stang but have a 351 swap in it. From what you described tho, it sounds exactly like the problem I had. Except your issue may be the alt. being too small rather than my problem of a drained battery. Had the charging system tested and see if the alt. is keeping up. If not, swap a new alt. in there that puts out more amps and you should be good to go!