| Problem | Likely cause | Fix | |---------|--------------|-----| | No power (LED off) | Blown fuse, bad ground | Check inline & remote fuse; measure GND | | Protect LED on | Short in speaker wire | Check bare wires touching chassis | | Low volume | Gain too low or HU low | Increase gain or HU volume | | Distortion | Gain too high | Reduce gain | | Alternator whine | Ground loop | Use better ground, add isolator | | Amp hot | Low impedance or airflow | Check load (min 2Ω), mount with space |