Does yours have the "dial" style fader in the dash? Either that may be bad, or if you have one speaker that is shorted out, the Alpine will shut off the power to the speakers (internally). Once you disconnect the bad speaker it should come back on. The Alpine has a common wiring color scheme.
Whites - Left Front
Grays - Right Front
Greens - Left Rear
Purples - Right Rear
All the black stripes are the negative. I would bypass the factory amp. If you want to use it, you need to hook up the blue with the white stripe up to the white wire (if I remember right) on the car side. This should turn on the factory amp. That being said, the Alpine radio puts out more and better power than the 20+ year old factory amplifier.
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