1992 aftermarket stereo

You don't need a wiring diagram because you will need to replace the o.e. speakers as well. The Alpine unit has a four ohm impedance output intended to reach four ohm coaxial speakers. O.E. junk speakers ar 1.2 ohms and not a match. You will want to wire the new speakers directly. DO NOT TAKE THE WIRES OFF THE O.E.ROTARY FADER ON THE CONSOLE. There is an electronic fader built into the Alpine head unit. The dirt-collecting rotary fader is rated at a max of 50 watts. P.