It's been ~30 years since I last replaced a car stereo myself. Last time was easy, it was a basic American make car - ~1970s vintage, and all the wires matched up on the old unit and the new unit.

Now I'm replacing the stereo in my 83 300d.

I'm doing this on the cheap, cheap, cheap. My new radio is a Dual system from Walmart. The Dual has a wiring harness and diagram in the install instructions, with the following wires:

1 - Blue (remote turn on) for power antenna or amp. (I replaced the power antenna with a non-powered antenna, and so I will not use this wire.)

2- Black = Ground

3- Red = Accessory (from ignition)

4 -Yellow = memory (direct hot to the battery)

The 4 wires that go into the plug (the numbers below are on the plug) for the Becker unit are:

1 Brown
2 Black
3 Gray
4 Red

Can someone tell me what these wires are coded for? I have the battery out of the car so I can't test for ground, hot, etc. I don't know if it's safe to assume black=ground or if Mercedes or Becker used some other wiring code in 1983.

Second, the speaker wires. The new unit has 8 wires for speakers, hot and ground for RF, LF, RR, LR. The becker unit had 2 plugs for speaker wire, each plug having 2 wires into it. The car ('83 300d) has 4 speakers and a fader switch in the center console, does this mean that the speakers are mono and I only have front and back, but no "right" or "left" in the current wiring? If so, would I just combine the right/left wire pairs from the Dual to wire up the front with both RL wires to the hot and both RL wires to the ground, ditto for the rear, and then end up with mono sound?

I am not an audiophile. I just want to get radio without sporadic static (current problem), and have a USB plug for my iPad. I can live with mono. The diesel is really noisy, stereo or better speakers probably won't make much difference considering how noisy it is in the car. I'm just trying to get this new stereo installed with the current speakers for now, and then I'll explore putting in better speakers if I'm unhappy with the results.