E3201998

The stock unit that's in the car

Wiring harness behind it

hey everybody,

I am looking for some insight on Mercedes e320 1998 audio upgrade, i am planning to overhaul the whole existing system completely as its finally gone kaput after 26 years. I am planning to install a new pioneer head unit which will drive 6 speakers directly or with a amp(whichever is easier for now) i plan on doing it in stages so right now my main concern is getting some of my audio back and then spend money on a amp/improvements later. I have been scouring the fourms and my basic understanding of the system is that the car comes with 2 diffrent sound systems, one is Bose and other one is the factory speaker system. I am not bothered by either of those as i want to change all speakers/amps /wires. I am looking for help related to the wiring aspect. I can do complex wiring but i was wondering if the existing witing could be used to feed signal to the speakers directly through the new headunit/amp(whichever is easier). How should i approach it ? I am getting 6 new speakers for my front/rear and rear tray so i am not sure how to go about installing everything. I am proficient at wiring but i haven't seen many pictures/tutorials of showing how the wiring is routed inside the trunk or in the head unit. I have found the wiring diagrams but my question still persists for using the old harness to send signal to new speakers/amp or to take it all out and put new wires in ?

Also another concern i found while reading the forums was that once a new aftermarket headunit was installed a fellow merc enthusiast was having problems with his central locking, he stated that once he put the new unit in everytime he opened the door the alarm went off. When he removed the aftermarket unit it didn't happen which completely puzzled me.

Any help or tutorials on the matter are appreciated, i rather not go to somebody and get it done as i plan to keep my car with me for a long time and i want to know how to fix things if they go wrong by myself. I have also emailed Mercedes benz for any insight and Crutchfield in case they can help me with anything (their manual turned out to be useless, 13 bucks down the drain)