Need help identifying wires behind radio

[ExploreHudson]

Hey all

My new to me 91 X came with an aftermarket headunit, but sound was only coming out of the front right speaker. And if i turned the volume up to a decent level it would cut out. I assumed the factory amp or headunit amp was toast. Purchased a new headunit and some 6x8 speakers.

Removed the head unit to find some interesting wiring. The 8 wire gray shielded speaker plug was unused entirely. Instead, the blue shielded wires pictured below were hooked up to the speaker wire outputs from the headunit. How was audio coming out of the front right speaker?

Okay.. next step was to bypass the factory amp.

Which on a 2 door is a huge PITA. Got in there and discovered the factory amp had been removed. And a bunch of splicing to the wiring back there. Was there a sound system that was maybe destructively removes at some point? Anyways, soldered everything back to stock and installed the bypass harness.

Went ahead and installed the same headunit adapter from the old one into the new one. Same result, sound only from the front right speaker.

Went back in, removed the blue shielded wires from the harness, and used the 8pin speaker plug adapter as specified. Double checked everything.

Reinstalled the dash and all, now i only get sound from the right rear.

I went ahead and installed a new speaker into each back seat and the same result.

Im scratching my head.. wtf is going on here?

Attached are some photos of the blue shielded wires and also of a random 2 wire connector dangling below the dash. Any idea what these are for?

Thanks in advance yall

 

[Jason94sport]

1990-91 Ford Explorer Stereo Wiring
Constant 12V+ Green/Yellow
Switched 12V+ Yellow/Black
Ground Black
Illumination Blue/Red
Dimmer n/a
Amplifier Remote Blue
Antenna Right Front
Front Speakers 5" x 7" Doors
Left Front (+) Orange/Green
Left Front (-) Blue/White
Right Front (+) White/Green
Right Front (-) Green/Orange
Rear Speakers 5" x 7" Rear Doors
Left Rear (+) Pink/Green
Left Rear (-) Brown/Yellow
Right Rear (+) Orange/Red
Right Rear (-) Black/White
I'm not sure if a 91 had an amp back there. The guy maybe had aftermarket speakers & just used the wiring back there to tap instead of pulling new wire. The dangling wire I think plugs into the back of the climate controls.

 

[BrooklynBay]

Check the schematics on Dead Link Removed.

 

[ExploreHudson]

Okay figured out the blue shielded 4-wire bundles were used as aftermarket speaker wires.. for what reason I have no idea, they re-spliced back into the factory speaker wiring down by the scuff plate covers. I really am at a loss for words in what was going on before.. I should have taken pictures of the wiring madness but I was impatient to get things sorted.

Fixed the splicing under each scuff plate and gained my front two speakers!

Now I am down to tracing the open circuit for the rear left speaker... wish me luck yall! If I can't get it in a day or two I'll just run new wire for that one speaker.

 

[ExploreHudson]

Question, what are those holes drilled into the bottom of my dash? Am I missing something or was that were they had a CB radio or stereo amplifier mounted? I believe the car had an antenna, found another really weird connector.

 

[ExploreHudson]

Bought one of those tone generators/continuity testers and was able to confirm that both wires are making it from the head unit to the speaker.

One odd thing.. when i have the tone generator connected to the positive speaker wire (with the speaker plugged in) and then to chassis ground, and I plug the metra adapter into the headunit (unpowered), i hear the tone through the speaker. What does this mean? Am I just completing the circuit for the speaker? Seems like it should make sound from the headunit but it does not.

So no real progress, going to just run a wire pair straight to this last speaker so i can be done with it.

One awesome tool added to the collection. Very useful for only $20, highly recommended

 

[Centaurious]

Sounds like a grounded speaker wire. Speaker wires must not be grounded or amplifier damage can occur.

 

[ExploreHudson]

Did a lot more poking around and found that the factory speaker harness connector at the headunit was cracked and that channel was the only one affected. I wiggled it until the sound got better and taped it into that position, hopefully it holds up. Now I have all 4 speakers, good to go!