GMC Cab & Chassis C3500 (1985-2000) Am/fm stereo, with cassette & amplifier

1 2 3 4 RF (+) RF (-) LF (+) LF (-) 17 18 19 20 RR (-) RR (+) LR (-) LR (+) 5 6 7 8 9 10 GROUND PARK LAMP DIMMER ANTENNA OUT IGNITION MEMORY ANTENNA BLK WIRE BLU WIRE BRN WIRE CASSETTE DECK CONVENIENCE CENTER (UNDER LEFT SIDE OF DASH) CTSY FUSE DK BLU WIRE DK GRN WIRE DK GRN/WHT WIRE FUSE BLOCK (UNDER LEFT SIDE OF DASH) GRAPHIC EQUALIZER GROUND PARK LAMP DIMMER IGNITION MEM (DATA) DATA GRY WIRE HOT AT ALL TIMES HOT IN ACCY OR RUN INTERIOR LIGHTS SYSTEM INTERIOR LIGHTS SYSTEM LEFT FRONT SPEAKER LEFT REAR SIDE DOOR SPEAKER LEFT REAR SPEAKER LT BLU WIRE LT GRN WIRE LT GRN/BLK WIRE LT GRN/WHT WIRE LT RR DOOR SPKR AMPLIFIER RELAY GROUND LT RR DOOR SPKR NOT USED LT RR SPKR LT RR SPKR RT RR DOOR SPKR NOT USED NOT USED ORG/ WIRE ORG/WHT WIRE PNK WIRE POWER AMPLIFIER RELAY (UNDER DASH, LEFT OF PEDAL BRACKET) PPL RADIO CONTROL HEAD RADIO FUSE RADIO POWER AMPLIFIER (UNDER DRIVER'S SEAT) RADIO RECEIVER RED WIRE RED/WHT WIRE RIGHT FRONT SPEAKER RIGHT REAR SIDE DOOR SPEAKER RIGHT REAR SPEAKER RT RR DOOR SPKR NOT USED NOT USED RT RR SPKR RT RR SPKR TAN WIRE WHT WIRE YEL WIRE