1990 gm c1500 pickup radio diagram?

I've got the three components out of a 1990 C1500 Chevy truck, want to know if anyone has the complete wiring diagram?  The radio has 3 parts, the amp, the radio, and the tape deck.  I want the wiring diagram for the wires between the tape deck & the amp, and the radio & the amp.  Need to know which wire(s) is the the trigger to make the amp switch from the radio to the tape deck.

Thanks.

Yes, they are connected & working right now.  So it will be +12 volts when the tape is inserted, and no voltage when the tape is removed?  If that's the case, that'd be great & easy to find.

Thanks for your help.

Yeah.  I've had the radio a long time mounted in a cooler on a boat.  Don't really use tapes any more (heh, since 1990), and I figured if I could make the amp switch to the aux input it would accept the input from a mini-phono jack.

Speaking of which, any suggestions on how I would identify the audio wires from the tape deck to the amp?

Thanks again.

Inside the wire bundle, there is a 3 wire shielded bundle.  It has an insulated white, insulated red, and bare black.  Think that's +left, +right and -common?  I was thinking that was power, but like your suggestion above, I guess that would be easy to test.

I'll take some pics and post results when I'm done, if it's successful.  Thanks again.

Got it, it was the brown wire.  Supplied +4.88 volts when the tape was inserted, 0 when the tape is ejected.  Should be simple now.  Short out the switch inside the tape deck, and put a switch in the brown wire.  Then wire a mini phono plug into the 3 wires in the shielded cable, and splice a 12 volt cig-lighter plug into the switched 12 volt supply wire.

Gotta find a plastic box to put it in now, maybe a cheap plastic toolbox.  Has to big enough to hold the radio parts & a lawn tractor battery.

I'll bookmark this page and post pics when it's done.

Thanks for your help.