Car Stereos: cant get amp to turn on

Question
I have a 1996 pathfinder and I cant get my amp to cut on. Ive run all wires correctly yet it seems the remote amp wire from amp to wiring harness isnt connected right. Ive run it to the blue amp turn on wire, to the blue and white power antenna wire,  and to both with no results. Please help as ive hooked up many systems and never encountered this problem.l

Answer
Hi Brandon,

To troubleshoot any amplifier power problem, you really need to have a digital multimeter to do it right.  The cheapest multimeter you can find will work perfectly well for this.  

Set the meter for DC volts--if it's not an autoranging type, use the 20V range.  With the system turned on, place the black probe on the amplifier's ground terminal, and use the red probe to test the voltage on the main power terminal and the remote terminal.  Both voltage readings should show above 11 volts.

If the power terminal voltage is low, check the connection at the battery and main fuse holder, and replace the fuse even if it doesn't appear blown.  If the remote terminal voltage is low, then there's a problem with the remote wire--check the connection at the head unit, and make sure the wire isn't pinched or shorted somewhere between the head unit and the amplifier.  If both terminals show low voltage measurements, then the most likely problem is with the ground connection.  If both readings show proper voltage, and the amp isn't turning on, then check the amp's built-in fuses; if they're good, then the amp itself is defective.

That's the generic amplifier power troubleshooting procedure, which I always pass along because it always works (at least to find the source of the problem).  Now I'll address some of the specific things in your question.

You don't say what kind of head unit you have.  The standard color of the power antenna output is solid blue; the remote turn-on output for the amplifier is blue/white.  However, these outputs have a fairly low current capacity, and there's usually a protective circuit built into the head unit.  That means if the wire is shorted somewhere along its route, there won't be any voltage on the wire until the situation is fixed.

You can use the multimeter to test the voltage right at the head unit.  If there's no voltage with the wire connected, but the voltage comes back when you disconnect the remote wire, then the wire is shorted somewhere along its length (or the amplifier has an internal remote terminal short, but this is rare).  On the other hand, if you find voltage at the head unit with the wire connected, but no voltage at the amplifier end, then there's a break in the wire somewhere.  (A puncture in the wire can let water in and corrode the wire inside the jacket, so the conductor is broken but the break isn't easily visible.  The way to test for this problem is to measure the voltage at different points along the wire).

That's why a multimeter is essential for this kind of troubleshooting--without it, all you can do is guess.  The one thing I'd suggest if you don't have access to a multimeter (other than go out and buy one) is to disconnect the remote wire at the amplifier, then use a short piece of wire to make a connection between the main power terminal and the remote terminal on the amp.  If the amp turns on with the jumper, then you can continue focusing on the remote wire as the source of the problem; if not, the problem lies elsewhere.

Hope this helps!

Brian