Car Stereos: Amp and sub trouble in Impala 03, dc volts, power terminals

Question
hello Brian,
I have recently installed a sub and amp in my 03' Impala. I ran a converter from the back speaker wires to get a signal. All seems to be well except for one major problem...... It keeps turning on and off. I forgot to mention i also installed a capacitor. I have the power wire run along the passangerside nd the rcas of course to the converter. The remote wire is tapped into the aux/cig fuse. Not sure the problem.. When it turns off, if i stop the car and turn the ignition off then back on the amp and sub work fine only to cut off again after a period of time. I was thinking maybe that fuze is not supplying power all the time or somthing simple of that nature. I have the ground ran from under the back seat. I found a large bolt comming up fron the posterior side of the car and just backed off the nut and grounded it there... What should I try? It sounds great when its working.. its just keeping it working that Im needing to accomplish.

Answer
Hi Bryan,

The main question is whether the amplifier is shutting down entirely, or if it's just going into a "protect" mode and shutting off the output.  When the amplifier isn't working, can you tell if there are any power lights on it?  Does the amplifier have a "protect" or "fault" indicator light?

A power problem is easier to solve, because you can test for voltage issues with a multimeter.  If the amplifier is completely dead with no lights or sound, use a multimeter to test the voltage at the amp's power terminals.  Set the meter for DC volts, put the black probe on the ground terminal, and touch the red probe to the power terminal.  You should get a reading around 12 volts; higher if the car is running.  Touch the red probe to the remote terminal, and you should see 12 volts here too.

If you get a low voltage on the power terminal, there may be a problem with the power wire.  Check for a loose connection at the battery, or at the fuse holder near the battery.  Change the fuse, even if it doesn't look blown.

If there's a low voltage on the remote terminal, then you'll need to look for a problem with the remote wire connection.

If you get a low voltage reading on both the power and remote terminals, that might mean that the ground wire isn't adequate.

On the other hand, if the amp is triggering a "protect" mode, it might be harder to track down the problem.  Usually an amplifier goes into protect because of an output problem--if it's wired to a subwoofer with too low an impedance rating, it might cause the amp to overheat and shut down.  A shorted speaker wire or defective sub can also cause an amplifier to shut down.

Hope this helps!

Brian