Why won't my car amplifier turn on?

[KaeZoo]

You really need a multimeter for any serious troubleshooting. A test light isn't accurate enough.

Your problem could be caused by a loose or corroded connection at the battery, a defective or blown power wire fuse, or a loose ground wire connection. I'd probably start by checking the battery connection, and replace the fuse on the power line near the battery, even if it looks good.

A capacitor won't fix a power problem, especially in a case where the amplifier isn't even turning on.

 

[kuroiryu42]

I install a car amplifier last January and now it won't turn on.
Not sure what could have changed. I bought a simple circuit tester
to see if it was still getting power. And it is. I also tested the trigger connection from the stereo and that seems active as well.

Thought it was a bad amp so got a new one. It won't turn on.
Suggestions?
Do I need a capacitor? If so why all of a sudden?
Car still starts up normally.