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Old 04-29-2018, 08:34 PM   #551
Advanced Member
Join Date: May 2016
Location: Oklahoma
Posts: 135
Did this re-wire tonight on my sonís 90 325is. The car has premium sound with no fader dial in the dash. Very bizarre wiring for what should be a very simple audio circuit.

From amp to speakers is a piece of cake and Lukeís original post is spot on. 4 speakers, 4 twisted pairs, 8 wires total. Easy.

The connection from the front of the car to the amp input is where things get confusing. Rather than sending 8 wires from the radio to the amp like any sane person would do, BMW opted to tie all the grounds together at both ends. Lucky for us, the twisted pairs still exist, you just have to untape the harness and work your way back until you find them. Keep in mind that the ground colors in the first post may not match your car. Youíll probably end up with 2 yellow/brown wires and 2 blue/brown. Just keep the twisted pairs together and connect one at a time.

Picture of our trunk wiring before we taped it all up with cloth harness tape. Hope this helps!

- Darrell

2001 BMW M5
1990 BMW 325is - Build Thread
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