I have a 98 f250 5.4 (not the heavy duty) And like 3 weeks ago my speakers were like shorting out, they would randomly shut off an flicker back on and my bass that I put in myself is the only thing that works. So I thought it was the deck/cd player that I had so I put in a different deck and it diddnt help. All the fuses in the fuse box look fine. The wiring directly behind the cd player is all fine. Now the speakers only work when either just the battery is on, or I am stopped, an sometimes when I am stopped or have the battery on they still dont work. It helps when you bang random things like the door or hitting the dash it flickers back on. I dont know what in the hell it is but I need to fix this or I'm going to go insane. I put new pioneer speakers in about a year ago. I dont know what it could be does anyone have a clue? Also When you turn the key all the way backwards to just put the stereo on, it doesnt work.

 

When your speakers cut off, is the CD player display still on? Is it an aftermarket headunit? If so, did you use a wiring adapter or cut the factory plug?

 

It doesn't sound like a "speaker" wiring problem, if the position of the ignition key has anything to do with it. It sounds more like a power supply to the CD player problem. If you answer yes to any of smaug's questions look at the power supply. Have you pulled the speakers to check the connection their? If they are coaxal, also check the jumper wires from the woofer to the tweeter.

 

Did you perchance run new wire through the rubber wireway into the door?

I did when I put my speakers into my old truck and it was an extremely tight fit. After a few years of opening and closing the door... I would get the same thing. Only mine were amped and it sounded like the speakers were going to blow out when they flickered.

It was from overflexing the wires in that boot and they eventually broke inside the insulation, shorting out and doing what you are talking about. I re-pulled new wire and it was fine until it broke again.

This was door speakers only, the ones behind the seats continued to work fine.

 

Also check your grounds to any amps you might be running. I had an intermittent problem with my sub and front speakers and ended up that the screw that the amps were grounded to had come loose. Once I tightened it back up, I have not had a problem since.