2007 Ford Focus ZX3, Remote Turn On & More

I have a 2007 Ford Focus ZX3 with a factory subwoofer and I am installing an aftermarket radio.

I ordered the WH-004 wire harness kit which includes:

1. Wiring harness/plug

2. Subwoofer harness/plug

3. A red single wire with a brass prong?

4. A resistor

Here are the instructions for connecting the resistor





My questions are:

1. What is the red wire and brass spade prong for?


2. In the instructions it says to connect the resistor to the "aftermarket amp turn on wire" which I hope is the "remote turn on +" coming from the aftermarket radio harness, is that right?

3. The instructions say to connect the "aftermarket amp turn on +" (WIRE 3?) to one end of the resistor, & connect the other end of the resistor to the two blue/white wires (WIRES 2 &3) **but** do I need to also connect the blue/white wire from the WH-004 harness the goes to the stock wiring harness (WIRE 4)?

Picture to show wire numbers:

I just ended up doing this, I hope it works.

Connect it to the 2 wires on the small plug. Should not be connected to the larger plug.

Some ford vehicles do not have a switched wire in the OEM harness. The radio turns on and off via DATA from the cars computer. The red wire is to run to the fuse box or some other switched source to turn the radio on and off with the key.