Car Stereos: Car Stereo Install, factory amps, digital multimeter

Question
I had a system put in my car its an aftermarket Kenwood stere but anyway i got a 400 watt amp on the install and it worked fine i decided to get another amp and speakers well i bought the kit for dual amps and when i connected everything i got no sound then i tried putting all the wires back the way they were and i got no sound at all now

Answer
Hi Edwin,

It's really difficult for me to say where the problem is without doing some testing in the vehicle, but when you have a head unit that turns on without producing any sound, then it usually comes down to one of three things:

1.  One of the speaker wires may be shorted, or a speaker may be blown.  If a speaker wire is shorted directly to another wire (as might happen if a speaker voice coil was shorted) or to chassis ground (if a wire gets pinched or cut against a metal surface) then it will cause the deck's internal amp to shut down, so you get no sound to any speaker.  The best way to troubleshoot this is with a digital multimeter set for resistance.  You'd probe each speaker wire at the head unit location, looking for low resistance to chassis ground, or a reading of 0 ohms when you're measuring the resistance between a positive wire and a negative wire.

2.  The vehicle may be equipped with a factory amp, which isn't working.  Many factory amps require voltage from your deck's remote output wire to turn on, so if the remote wire was overloaded by the new amp, then it might not be turning on the factory amp any more.  You'd want to test the remote output with the multimeter, looking for around 12 volts when the head unit is switched on.  You can also check your vehicle's fuse box for an amplifier fuse.

3.  The head unit's internal amplifier may have been damaged.  If you installed the new amp, and somehow had it so that one or more speakers was connected to the new amplifier AND to the head unit at the same time, the amp's output could have damaged the head unit's output through the speaker wires.

You really need access to a multimeter for any serious troubleshooting.  The key to troubleshooting is the process of elimination.  Disconnect everything except the head unit and speakers.  If you can't get it to work, try connecting just one speaker directly to the head unit through its own wire.  If that doesn't work, then it's likely that your head unit has a problem.  If it does work, you can start connecting speakers again until you find the connection that shuts it down.

Hope this helps!

Brian