What radio is correct for 82 240d
 

I want to put back the original radio. Also do the radios for 82 have seperat amps

Becker 599. Does not use a separate amp.

There were actually 2 radios available for that era.
The 599 as mentioned above, which is the total analog radio/cassette with the two big knobs.
There was offered as an upgrade the 612 which is a first generation digital tuned radio/cassette.

If you upgrade to the 612 fish around under the radio pocket, you will find a two pin connector. One pin is the constant hot (circuit 30) from fuse 2 for the memory backup and the other is circuit 58 for the dash lights from the rheostat.

The 599 just had a switched hot and ground. The internal light was on all the time it was on. And of course it did not need any constant power, so it just had the one power connection.

Neither of these had a separate amp or tuner module. That did not arrive until about 1990 with the 124/second gen 126. These radios have 2 speaker outputs that went down to the fader in the console and out from there to the speakers.

The rear speakers were an option. The stock configuration just has the 2 plugs from the dash speakers landed behind the radio. If the rear speaker was selected, the fader was provided. Its harness has 2 plugs that go into the radio, and 2 sockets to receive the plugs from the dash speakers, and 2 more sockets to receive the wires going to the back deck (sedan) or rear doors (wagon).

Becker Auto Sound still exists even though they have been bought out by Hartman/Kardon. They maintain an office and repair depot in New Jersey. If you find a radio in a JY (that hasn't been trashed, for some reason every original MB radio I find in the JY gets trashed by the time I get there) send it to Becker to get fixed. Or you can sell it to them for core value. Look up beckerautosound.com for their info.

Um... my 78 300D had a becker mexico with a separate booster/speaker balance box...

From what I found out researching this when I had a 123, they did start off in 76 at the introduction with the Mexico (which is what was in the 115/116).

But by the early 80s (not sure what the break point was) they had transitioned to the 599/612. Probably the same time they made the mid cycle refresh that changed the hazard switch from the push button to a rocker switch, air conditioner control from a rotary to a wheel knob, two sliders on the climate instead of one, and so on.

I think the 612 was the standard radio for the 126 at this point.