well, about 90% done with my system install and noticing a wierd problem. when my car is off and i'm just running the system, the sub plays nice and loud. however, when i turn the car on, it gets quieter. it does however get louder for short periods of time when things such as brakelights, turn signals, and turning the headlights on. I've been workin on systems for over 4 years, and this is the first time anything like this has happened. i ran a brand new 2 ga wire from the battery to the chassis and cleaned up my grounding spot for the amp (big trunk latch bolt). anyone have a better place to ground it? i have a feeling it has something to do with the grounding, because another amp in the car did the same thing.

 

thats where I ground mine. it works perfectly fine.

 

use an ohm-meter to check the ground,measure the voltage at the power terminals when the car is on and off. check the head unit low level out puts too (AC low voltage on the multi meter,or osciloscope)