i'm trying to replace the original radio in a 78 300d.

the wires that are available in the car are:

red
blue w/ yellow stripe
brown
speaker wires
antenna wire

the replacement radio i'm trying to install has the following wires:

yellow - identified as "battery +12v"
red - identified as "turn on +acc"
black - identified as "ground"
dark blue - identified as "power antenna"
antenna
speaker wires

my issue is, where to plug the yellow and red wires from the radio to the car.

thanks for the help.

The easiest way to match up your yellow wire is to test for 12V from the existing harness with the key off. Use a test 12V light, one end to the brown wire connector pin (ground) and the other to either the red or blue with yellow stripe wire. If it lights up with the ign key off, that's your yellow wire. Do the same for the red wire, this time with the key in the first ACC position. Key off should turn the light out, key on in position 1 should turn it on. You could also use a multi-tester to see 12V.

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1986 560SL
2002 Toyota Camry
1993 Lexus

A good place to tap for that yellow wire is to remove the 4 way flasher behind the shifter and tap into that as it is constant....You will still need a test light to do so however....

__________________
83 300CDTurbo 307,000
2005 Honda Element 266,000
56 Nash Ambassador Country Club Special 34,000(under restoration presently)

http://www.peachparts.com/shopforum/car-audio-multimedia/125099-123-install-extreme-dynamat.html

Just done mine in an 83 280sl. Same wiring.
the wires that are available in the car are:

red - As stated power from your old radio- Join to red of new headdeck.
blue w/ yellow stripe - Factory electric aerial - connect to Dark Blue new head unit.
brown - Current earth- normally two - attach to bolt on rear of new head unit.
NEW YELLOW} This is the new wire on your replacement head deck, you will have to connect it directly to the battery (with an inline fuse) OR join with scotch lock to any wire that has CONSTANT power in your wiring loom (with the ignition off) It needs constant power for the memory -time, station pre-sets, etc. Speaker wires should be easy, plain = generally earth/neg, plain with trace Pos.
NEW BLACK] Off headdeck - Screw to steel body panel or join with existing mercedes brown earth wire, doesn't really matter. Problem solved!