Random Thump Noise

I have a random "thump" noise that I just can't seem to isolate. It is random which makes it a real pain. This is what I know about it so far: (1) It occurs in tuner and CD mode (2) Is independent of volume level (3) Does not cause my amp's "short" light to come on which       would indicate a short circuit. (4) The ground screw is attached to the sheetmetal of the      truck. Paint was ground off down to bare metal then       screw was attached. My cheap amp meter indicates       zero ohms resistance back to the ground. Does anyone have any idea as to what my problem is? Thanks, Mike 2000 F150 Supercab Lariat, Alpine CDA-9831, Polk MMC570 in Doors, One Polk MM2104 Sub, One Polk Carbon C400.4 Amp.

John 3:16

Swap out head unit. I had same problem and covered it up with a noise filter until my head unit just died. So try to isolate it by swapping out the deck.Tell the Snap-On guy I'm not here!

What type of head unit did you have? Did the noise return when you installed the new head unit minus the noise filter?2000 F150 Supercab Lariat, Alpine CDA-9831, Polk MMC570 in Doors, One Polk MM2104 Sub, One Polk Carbon C400.4 Amp.

John 3:16

Had clarion, No noise didn't return. I think the deck got overheated.Tell the Snap-On guy I'm not here!

I had the head unit installed a few months before I purchased my amp and sub. I listened to it every day but never heard the thump noise until I installed my amp and sub. Could it be that the sound was there but it was inaudible through my factory door speakers? Is there a way to eliminate the amp as the problem? Mike 2000 F150 Supercab Lariat, Alpine CDA-9831, Polk MMC570 in Doors, One Polk MM2104 Sub, One Polk Carbon C400.4 Amp.

John 3:16

It could be. Was it a refurbished head unit? You might wanna check your rca cables too. But yeah I didn't hear the noise until I got a JL 500.1 and 10W7. It just picked up the low freq tump and amplified it till it was unbearable.Tell the Snap-On guy I'm not here!

No, the head unit was new from Circuit City. Is there a way to check patch cables to see if they are good? What does one check for? What can one check for in patch cables? Mike 2000 F150 Supercab Lariat, Alpine CDA-9831, Polk MMC570 in Doors, One Polk MM2104 Sub, One Polk Carbon C400.4 Amp.

John 3:16

Loose connections. Take it back to circuit city.Tell the Snap-On guy I'm not here!