can someone please explain to me how the stock sterio wiring in an '87 4runner works? a wiring diagram would be helpful too.

sterio is all stock (except a panasonic cd player), with rear speakers. rear speakers are not working, which is pretty much what im trying to figure out at the moment.

But, the wiring has me a little confused. Ive done plenty of sterio and electrical work, but i dont understand what a bunch of these "extra" wires are doing.

first of all, theres 2 connectors at the rear speakers. 3 wires in one, 2 in the other.

second, under the dash, theres the 2 normal connectors: one with power/ ground and front speakers, and one with rear speaker wires.

There is ALSO another connector, same as the "main" connector (with power and ground) that goes into some sort of a jumper harness.

what really confuses me, is BOTH the connectors work, as in, the sterio works (with just front speakers) with either of the large connectors plugged in. AND it dosent matter if the other large connector is plugged into the jumper harness or not.

If anyone can make sense of what im saying, please help, im mega confused.