Like any electronic product, things do go wrong at times with amps. Regular or intense usage eventually causes problems to occur, which can be sometimes fixed. So before you through your old amp out, try to find out what the problem is and the cause, then see if it can be fixed.
Problem 1: Not Turned On
It may seem silly, but often the reason why an amp is not working is because the gain level is not turned on. If the gain level is not on, no sound from the speakers will be produced.
Problem 2: Wiring
A short circuit is a common problem in all well used electrical goods. It can be usually detected by the fact that the amp jumps between on and off or completely fails. Have a look if the any of the wires appear to be broken, causing a short circuit. A preventative action is to reframe from placing wires near any sharp edges, alleviating the risk of short circuits.
Moreover, check all wires connections, from amp to speakers to stereo to car, as any one of those wires could be the source of the problem.
Problem 3: Fuses
Fuses can also be the cause of your amp not working in your car audio system. A fuse on an amp is usually located near or on the power side. Check the amps fuse and if blown, find out a professional to replace your amps fuse. If the fuse keeps blowing, there is clearly a major problem with your amp, which probably means you will have to replace it.
Problem 4: Over Heating
If you use your car audio system intensely, you may find your amp cuts out.
Over heating in some models causes permanent damage, yet, some models (usually from Pioneer) have a function that turns off the amplifier when overheated, protecting it from damage. If you have a model with this function, simply wait till it cools down and resets itself. If you dont have this protective function, simply let it cool down and test it out again. If it works, try to use your car audio system a bit more carefully in the future and leave your amplifier in a ventilated area. It may also be worth investing in an amp with cool down functions, which regulates the amps interior temperature, making sure no damage through heat comes to the interior components.
There are other various reasons why your car audio amp many not work, which are fixable and are not. If you cant find the problem, either take it to a car audio specialist or replace your car amplifier.