I need some help guys I've checked all required accessory fuses and relays and they're all good to go but my headunit still won't turn on. I went as far as straight wiring my headunit to the battery to see if it was fried but the headunit started right up. So now that it's in the dash all plugged up it will not turn on. Anybody got any ideas? Has this happened to anyone else? It's a 2004 Ford F-150 lariat 5.4L.

 

Did you check the radio fuse?

 

If you powered the unit up that means you know what pin is power. Therefore you know what wire is placed in that pin connector, id trace the wire back and or test for continuity and power. As Bucko said check stupid stuff first, radio fuse, accessory plug fuses etc...

With every vehicle I get, I always buy a Haynes manual because they got great schematics in the back.