I bought an '83 300CD that came with a cell phone antenna stuck in the old mast tube. Fortunately the owner provided the original Hirschmann antenna as a spare part.

I installed a new mast and dry-fit it to test it works, but I have no idea how the old antenna was mounted. The wires from the old antenna were loose and were not in a connector. I found a connector in one box, then possibly the back of the connector attached to a mounting bracket in another box, so now I'm trying to fit them all together and mount them behind the sunroof teleflex cable.

I think I can see which hole the lower bracket mount uses, but how are the wires routed? They don't seem long enough, unless I'm missing something.

I've searched the forum and found pics from another model, but nothing on the W123. I assume the coupe and the sedan are similar enough in the rear fenderwell.

I've got a Hirschmann 6000U with a short length of wires out the top near the mast, an angled bracket with Philips screw on the bottom along with a basically rectangular hole with notches for what could be an electrical connector, a electrical connector back attached to a metal brace with a hole and two dimples that look like they should align to some square corner and be attached by a screw, and the factory harness.

The factory harness does not easily reach to the antenna wires. It reaches, but barely, and if connected then the metal bracket with the dimples it doesn't fit anywhere. I'm not even sure the parts all go together, they were merely close enough together in the boxes of spare/old parts provided by the PO. I haven't found any other parts that would complete the install.

Any takers on providing a pic? Or just telling me I'm trying to arrange a mismatch of parts?

Joe Y.

After a visit to the worst junkyards in the world ($150 for a used 25-year old cruise control amplifier? YGBSM!!) I figured it out.

I checked the hulks in the yard and saw two different mounting schemes in 123s. There's a short-pigtail/high-mount and a long-pigtail/low-mount. My problem was that I had a short-pigtail antenna (6000U) and a low-mount car ('83 300 CD, w/ electric sunroof) so the cord from the antenna couldn't reach the plug on the car's harness. Never assume the PO gave you the original factory parts...

I don't know if it's a model-year thing or an electric sunroof thing that determines whether it's a high- or low- mount. It's not a coupe thing, since I saw the two set-ups on sedans.

Fortunately, the MB wiring harness in the coupe has enough slack that it could accomodate either. I simply moved the grounding point on that harness about 5-6 inches higher up on the fenderwell seam. The bolted-in grounding point was the limiting factor in the location of the antenna plug.

Pic 1 shows the short antenna cord (pigtail) attached to a bracket on the top of the antenna. If you look closely you can also see a rectangular connector-cutout on the bottom galvanized antenna bracket. And that's only dirt/dust in the bottom of the fenderwell, no rust whatsoever back there.

Pic 2 shows the harness plug in the factory position not quite reaching the antenna connector.

Pic 3 shows the re-routed cable connected to the antenna. You'll note the loose screw at the end of the brown ground wires. I moved this fitting from a hole that is out-of-frame from the pic and will tighten it down when I'm finished. You also get a better view of where the long pigtail would connect. On some antennas, the longer cord would go down the left side of the motor casing and connect at the square rectangle.

Joe Y.

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Joe:
In pic 1 there is a black wire with a circular end lying in he well. What is it for and where does it go. I am having trouble with reception (Grand Prix) and hope this has something to do with it. Mine is not connected and I hope this has something to do with it.
Thanks...Jim

That may be a hard wire for an optional phone antenna.

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83 SD

84 CD

toomany is probably correct, the black co-ax wire is probably for a cell phone. I think the other end of the black wire is near the glove box. I've never bothered to follow it all the way back. You should be able to ignore it.

The factory antenna wire is the grey co-ax just above the black wire in pic 1. It attaches to the 'fork' in the antenna in the top center in the same pic. The other end of the grey co-ax wire is behind the radio in the console.

If both ends of the grey co-ax are connected to radio and antenna, respectively, then the problem 'might' be poor connections between the aluminum collar, the antenna mast, and/or the ground. I think that collar with the antenna port is a slip fitting, so make sure that it's snug on the aluminum tube that connects it to the motor housing (or it might be theaded, so maybe try loosening the set screw, then spinning the tube to see if it tightens into place). Then make sure the set screw that holds the tube in place is tight (enough to hold the tube in place but not super torqued down) then make sure the motor is ground to the frame by both the brown bundle and the antenna bracket itself.

I'd also plug/unplug the grey co-ax behind the radio a few times to loosen any possible corrosion at that end.

Pic 3 is a dry-fit pic and does not show the grey co-ax connected, but you can see where it would go in pic 2. The metal tube running sideways across the pictures is the sunroof teleflex cable housing. Try to leave this alone if you're messing with your antenna.

Thanks to the DIY and all its pictures, I removed the antenna unit from my '81 240D today and opened it up to find out if the mast is the smooth or toothed kind. It's smooth, so I ordered a new one. The mast and white plastic cable has been gone since I bought the car. The motor runs, so I hope a new mast will put me back in business.

I'm so thankful for the amazing amount of information on the forum. Without it I would never have the nerve to do work like this on the car. I'd end up paying someone to do a mediocre job. Thank you all for the amazing spirit of sharing.