So I finally decided to install an after market stereo in my 84 300D, PO had removed the stock and install an after market. but the fader wheel on the center counsel was not wire properly. Hence rear speaker did not sound good.

How do I connect all the speaker wires from the after market stereo with four sets of wires to the two sets of wires for the stock stereo with the fader on the counsel functioning.

Right now just to have sound, I have the front speaker wires from the after market stereo connected to the two sets of wires. the rear speaker are getting something but not as good as the front. None of the rear speaker wires from the after market stereo are connected.

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1984 300D, 1972 LT1 Corvette, 2014 Artic White 3LT/Z51 C7, 2013 650i Convertible BMW, 1994 Kawasaki Vulcan, 1992 Yamaha Seca II and 1996 Dodge Ram 2500.