Stereo & Electronics - sub does nothing

I have a friend who has a kenwood amp and a sony xplod sub. He had it at less than halfway on the volume and the sub just stopped working and doesnt work now. What would be the prob and how could i fix it?

bad ground would be my guess... your ground has to be on the floor since our cars are unibodies.

its not my car and other systems work fine

Disconnect the speaker and put a AAA battery across the speaker and see if the speaker moves or makes any noise.

That is a quick test to see if it's blown.

(no movement or noise, it's history)

I am taking for granted the amp lights up or appears to work.

If the speaker is ok, reconnect to the amp and try a different input to the amp.

Just work backwards from the speaker.

got it one of the wires inside the sub came off so i hooked it back up and it works.

It sounds like the amplifier is bad, my buddy had 2brand new 15's kicker solo X's and had 2 brand new kicker 2500/or 1500 amplifier (dont remember but it was big) but this was a brand new system and we couldnt figure out what was going on cause the both amps turned on the safety lights were on and everything come to find out when he sent the amp back and got a new one it works fine, so that would be my guess good luck man.

use a voltmeter and check the resistance on the voicecoils...check the amp output voltages, check grounds..check fuses on the amp, check amp line fuse, has to be one of those

Okay everyone... the OP has already posted that he found the problem and fixed it.
got it one of the wires inside the sub came off so i hooked it back up and it works.

There is no reason to keep offering fixes for a solved problem.