[MikeS500]

I'd appreciate any help with this:

I bought an aftermarket power antenna to replace my broken stock one (95 S500 sedan). The stock unit has a wiring harness with 4 wires: blue, black, red/white and brown.
The blue goes to the splitter, which I don't need and won't be using. I would presume that the black is earth, the red/white is positive, and the brown is the signal from the radio. Can anyone confirm that with certainty?

Also, the stock unit has an earth (ground) cable going from the metal antenna directly to the fender. My new antenna doesn't have a mounting point for this and I'm wondering how necessary it is since it's grounded through the other wiring (the black wire).
Thanks!

Mike

 

[MikeS500]

So...Not one of the 21 people who read this thread knows which wires are which? Wow! Oh well.

 

[larsjoler]

Just changed my power antenna unit and had a lot of trouble but solved a mystery :

New unit has just 3 cables :

Earth ( always black )
Red ( constant positive )( to retract )
Green ( positive only with radio on )( to extend)

When trying to identify the original cables found in my 500SEL 1992 i found that they changed polarity depending on radio on or off, and that was not suitable for my new antenna unit. Tracing the original cables I found the culprit : a relay was switching over the polarity so that the original Hirschmann antenna unit would manage to go either up or down this way. Modern type units do have this relay built in. So after removing this newfound relay I found I now had also one green and one red coming from the car, so I had the new antena unit up and running in no time.

Back to the current problem :

You dont mention the antenna brand name nor the cable colors of this new unit but my guess is that you will have same configuration as my unit.

To identify the original cables from the car :

Identify first the earth/negative cable for sure ( yes it SHOULD be the black one ) : use a multimeter for this by either using the diode-check function or ohm-meter ( or just a lamp )

Then check polariy of the other cables when switching radio on and off. ( if you get reversed polarities then you too will have a switch-over relay somewhere !!)

My guess is that the red/white is the one with continuous +12V, and the brown or blue is +12V when you switch on the radio.

However, once you have identified the negative lead and connected properly ( also to the extra black one you have in the unit )then you can connect the other two in a trial and error test : if the antenna comes up when you switch on the radio, you got it right first on, otherwise just interchange the two connections...

 

[MikeS500]

Thank you for sharing your knowledge. Well, yes the new unit was a $25 Ebay antenna, with red/black/green wires.
I think it was defective, because even after giving it power, the relay on it just buzzed and the antenna wouldn't rise.

After all this, I found that the problem with the stock unit was bad corrosion in the connectors. Cleaned them, and now it works. However, in my haste to remove the stock unit, I cut off the antenna mast nylon wire. So, now I'm ordering a new stock mast and am going to write this one off to experience. Thanks again.

Mike

 

[Merc-S600]

For the power, red is permanent 12V, black is ignition, brown is ground at the radio that is , antenas ground could also b brown , b carefull