The first thing to check is the RCA connections at the amp. If the left side cut out, swap the left and right RCAs and see if the right side cuts out. If that doesn't solve anything, disconnect the speakers from the amp and tap the positive and negative leads of the speaker wire to a 9 Volt battery. The speakers should pop. If they do, use a multimeter to test the Ohms and also check to see if a wire is grounding out somewhere (the wire will read very close to zero with one probe grounded to metal and the other on one side of a speaker wire if there's a short). What kind of Amp is it? Most require the remote wire because it turns the amp on. Some (rare) have a music or signal sense feature built-in which turn the amp on.
