[Cunningr]

The problem with that specific amp is the rear channels power door speakers which are subs, and that channel has a frequency filter to only send the bass to the door speakers.

I suggest buying a 6 channel from a cabriolet, then run speaker wires from rear to front. The fader will then work, and the doors still work as subs.

As a note if you spliced front and rear it would affect the speaker load and no fader. If you used the rear channel eliminating doors you would have no upper frequency range.