Initially, they did wire through the stock fader. I had instructed them to bypass the fader, as the headunit had a fader control built in, and the fader switch was not rated for the amperage that the new radios put out . . . which would result in melting the fader switch, possibly starting a fire. But . . .what do I know . . . am just a dumb truck driver, and a woman to boot. So the tech who installed the radio that I had selected, ignored the written instructions, used the existing wiring setup (through the fader switch) and almost melted the switch/caused a fire. The next day, I drove across LA, back to the same shop, with the invoice that had my directions, and the fight started!!! They wanted to charge me for running the wires the way I had directed (it was a one-wire system, and needed to be replaced with heavier gauge speaker wire to the back, bypassing the fader switch). I refused to pay for that, de novo. I finally agreed to pay the difference in price for the wiring job, if they had done it at the same time as the radio installation (I think about $15 more). They had to tear up everything all over again, remove the seats and make under the carpet available, pull the headunit out, disconnect the back speaker wires, etc., etc.) The same tech was assigned the job, and was clearly unhappy, but was surprised to feel that the fader switch was sooooo hot and ready to melt, that he acquiesced and did the job, despite the little compensation he would get. But it seems, no matter what setup, or which car (190D, 240D, or the 300D), the sound is absorbed by the back windshield, and doesn't travel well to the front, which is why I later added the amp and box speakers behind me. It was the same amp and box speakers I had set up in the 190D when I encountered the same problem.

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1983 300D, the "Avocado"
1976 240D, 4-spd the "Pumpkin", SOLD to Pierre
1984 190D, 2.2L, 5-spd, my intro to MBZ diesels, crashed into in 2002