Your 8ohm channel is fried why happened was you ran 2 12s in an 8ohm load and turned it down to 2ohms the speakers was pulling all the power and that made it over heat and when it over heated it fried you're amp. It ain't no good you can't fix that
When an amplifier causes trouble or otherwise stops working, it is necessary to eliminate external possibilities such as a short circuited output.
If nothing external is causing the problem, unless you have a good friend who is an electronics engineer, it will be a repair shop task...
Double check your connections. Sounds like you are picking up alternator whine. Make sure the rca cable is at least 12" away from power and remote cables when installing fem radio towards amp. Its best to runthem on opposite sides.
.A thumbs up would be greatly appreciated if this answer is helpful to you.
Check your fuses. Check to see if any of the wires are loose. Could be a blown fuse or loose wire.
Possibly the following link might be of interest:
https://www.youtube.com/watch?v=xMbsieEj0UM
The spark is normal since at the initial time of the connection, the capacitor has 'zero' ohms. As it charges, less and less current flows until it is fully charged.The only way to 'pre-charge' a capacitor is to connect it to power.You can put a resistor in series and slow the charging rate and thus the spark will decrease/go away.Pick a high ohm maybe 1watt resistor, put it in series and go for it.