Okay i got the right wiring harness for the factory subwoofer where do i need to connect the blue wires that came on the new harness!!??? I dont wanna overload a wire. Its a 2004 f150 supercab

 

Blue is the amp turn on so you need to connect it to the remote turn on from the head unit.... but the stock amp/sub is a 5V turn on and will thump when the stereo is turned on. Aftermarket head units use a 12V remote turn on and the stock amp is expecting 5V, so it causes problems. You need to install a 5V voltage regulator to reduce the voltage

Radio Shack: http://www.radioshack.com/product/in...ductId=2062599

 

how do i install the regulator?? thanks for the tip i hate that thump noise!

 

I just did an aftermarket head unit swap tonite. Just got done as a matter of fact. I took a 6 disc changer out of my wife's Escape and put her in an Alpine with bluetooth and Ipod hook up.
You are correct about the thump. The stereo shop gave me a little resistor/capacitor or something that they use to drop the voltage down to a safe level. It had 3 pins on it. One was ground and the other two were what I used. I just used some wires from an old Metra wire harness kit that was left over from my pickup and they fit on the pins really good. I then put some shrink tubing on it and held it in front of my bullet heater in my shop and it shrunk right around it. No thump when you turn the key on now.
I measured the voltage coming out of it, and it was around 8 volts. I guess that was enough to kill the thump.

I am not sure why Ford uses the lower voltage amp on. Everyone else uses 12 volt. Seems dumb to me.
This thing had the factory sub in the back.
I took the blue remote on wire from the h/u and wired that to the top blue wire on the Metra adaptor harness, and it came on and worked.