wierd speaker problem?

My speakers in my car every once and a while get louder like they are cutting in and out but they are all working like it gets loud and then quiet. I listened to all of them and tried to find out if i had a dead speaker but they all have music coming from them? Anyone have a idea

loose wiring somewhere

do they ALL change in volume, or just one?

does your car have the fader toggle by the shifter like mine did?

yup the fader toggle switch works I have tried to I have to listen to figure out which speaker changes. I pulled out the cubby under the head unit and looked at some wires and none looked loose, but maybe the amp in the head unit is on its way out?

it could be the ehadunit, but those speakers are all common groud, and if i remember correctly, they are grounded to the fader switch somehow. even though it still works, there may be a short in it involving the grounds, mine started doing that, so i just got new speakers and a new headunit and re-wired the car (so it was no longer common ground and eliminates the fader switch) and it was fine.