89 Mercedes 420 SEL: How to Wire the Radio

1. Disconnect the negative cable from the car battery terminal, using an adjustable wrench.
2. Remove the two Phillips screws that hold the ashtray bracket. Pull out the ashtray, and unplug the lighter and ashtray light. Slide your finger below the radio to locate two steel tabs. Pull these tabs down individually, and use a flat head screwdriver to prevent them from re-engaging. Pull the radio out of the dashboard housing. Disconnect the wire harnesses, and pull out the black radio antenna cable.
3. Slide the radio installation sleeve, provided with the new radio, into the vacant dashboard housing. Bend the tabs on the side of the sleeve 90 degrees to secure it in place. Ensure the radio wiring can come through the portal of the sleeve.
4. Connect the wire harnesses of the 420 SEL to a wire harness adapter. Push the connections together until they snap into place. Repeat this process connecting the other end of the wire harness adapter to the wire harness of the new car stereo unit. Plug the radio antenna cable into the designated port on the rear of the new stereo unit.
5. Slide the connected new stereo into the radio installation sleeve until it clicks into place. Reconnect the lighter and ashtray light. Replace the ashtray and screws securing it.
6. Reconnect the car battery. Turn on the radio, and test its features.