I have a JBL 4 channel amp powering two 5.25" components in the front and one 12" sub (bridged) in the rear. It started the other day while driving, the amp would cut out, i.e. the red light came on on the amp and the green light went out. After a couple of seconds it would come back on, then off, then on, etc. However, as soon as I put the balance all the way to the front, the amp would not cut out, so it makes me think that the front channels are fine? I went out today and started messing around with it, and unhooked the left side inputs (line level) then the sub seemed to work fine for awhile. I began running new wire, then I was about half done and then it cut out again. So then I just started turning the frequencies and levels way down, but now I basically don't hear the sub. Also, somehow I no longer have power to my front left speaker. By moving the balance from left to right, my left speaker works, at left, nothing at center, then left speaker when balance is all the way to the right. What have I done??????? Sorry for the long message.

Do you have another amp to test with? all 4 speakers would have to be blown, I'm guessing the amp?

The front speakers are still working off of the front channels (with the exception that the left speaker is always on)

I don't have another amp to test with either. That would be the best way to test the sub I guess. Is there any way to test the power coming out of the amp?

swap the front and subs around...will tell ya something?

its deffinately the amp, speakers dont just quit making noise, they just sound like crap when they completely go, try fooling with it some more u might get it

Something may be bridging the connections, and that sends it into protection mode (I assume that'* what'* happening.

what do you mean by bridging the connections?

could this also be causing only the front left speaker to work all the time and front right not at all?

What the fronts have problems too? Check all connections. When i say bridge, i mean somethig is crossing the negative and postive wires. My first sub box ever, the wire hookup was bridged somehow, so i had to put a new one in. but if you got subs and a front channel out, your amp may be going. I'd recommend 2 amps to replace it. What are the ratings, and loads you are putting on the amp?

This what Bonnememn said is the answer. Your amp is not brideable and it overleads and goes into protection if it is. You need to unbridge the connection and youll be fine. If that isnt making enough noise for you youll have to get another amp. :?

ok, well that sucks donkey balls.... I do know that my amp is bridgeable (jbl 80.4). I will have to try running some new wire I guess.