1986 Mercedes 300 SDL Radio Wiring - What is the color of the constant hot? - PeachParts Mercedes-Benz Forum

ron59b · #1 09-06-2014, 04:34 PM

Good evening all

I am replacing my non-working Becker radio and I need to know which wire is the constant hot? I also need to know the color of the remote antenna hot, the function of the violet and gray and the blacl and white wire? My antenna isn't working either.

Thanks for any help offered.....

Ron

*some of the wires in the harness that runs to the dash are brittle. Which one operates the spedo and clock?

STORMINORMAN · #2 09-07-2014, 04:06 PM

Depending on which radio you had originally there are a couple possibilities: if these are the only wires, then...

BROWN on most of the MB radios is almost always GROUND

RED/WHITE s/b constant 12v+

A single BLUE wire, usually in a separate black sheath is usually the antenna

VIOLET/GRAY & WHITE /BLACK in your case are most probably the radio's "front" (main, if you prefer) left and right (+) channels.

If you have a fader there are probably 6/8 wires attached: usually this would be the 2 channels coming in and 4 going back.

No fader means you probably don't have the rear amps: is there a fader on the old radio?

GOOD IDEA TO TRY AND LOCATE THE MB WIRING DIAGRAM FOR YOUR YEAR AND RADIO: You could try putting power and a ground to the new unit and see if the lights come on and antenna responds. Then see if you can get sound from a speaker.

GOOD LUCK!

ron59b · #3 09-07-2014, 05:59 PM

Thank you for your response. I have power to the radio and sound from all four speakers. I am still working on power for the antenna.

Ron

STORMINORMAN · #4 09-08-2014, 01:09 PM

Good news: you can always try to run a 12v+ and - line (i.e., a piece of speaker wire or lampcord?) from the battery directly to the antenna to see if the motor is actually functioning..

ron59b · #5 09-08-2014, 09:03 PM

Thanks for that idea.

ron59b · #6 09-13-2014, 09:23 PM

I haven't found a good countious hot wire, and I had to disconnect the power from the antenna. The continuous hot, antenna, and accessory wires from the radio are all hooked to the accessory wire on the car. When the antenna was hooked up, the signals and instrument light would not work. Once I disconnected the antenna, the signals and other lights worked.

When the passenger door is closed or slammed, the radio and auxiliary lights fuse blows. This has happened twice. Any suggested of what to check? I'm planning to look into it all tomorrow.

Thanks

Ron

ron59b · #7 09-14-2014, 08:44 PM

Correction: I checked the fuse and it isn't blown. What seems to be happening is when the door is slammed, the system shuts down for some time. Any suggestions from the forum?

Ron

ron59b · #8 10-04-2014, 11:26 AM

I've checked many things and still can not get the wiring correct. I wired the radio to a constant hot and the accessory lights still only come on with the doors open. With the constant hot hooked to the radio, the radio works but also cuts off and on when the volume is turned up.

Any advice would be helpful.

tinypanzer · #9 10-09-2014, 02:02 PM

Quote:

Originally Posted by ron59b

I've checked many things and still can not get the wiring correct. I wired the radio to a constant hot and the accessory lights still only come on with the doors open. With the constant hot hooked to the radio, the radio works but also cuts off and on when the volume is turned up.

Any advice would be helpful.

Hmm, something isn't right. The radio cutting off when volume is up is the most worrying part. It almost sounds like there isn't enough current available on that circuit, and when the radio cranks up, the voltage drops to an unusable level. I would want to hook up a meter and measure the voltage on that wire, and see if it drops appreciably when the radio gets louder. If so, there is a bad connection somewhere upstream that is causing a bad current related voltage drop.