Problem with the R129 Sony radio.

[QuirkEinstein]

Hello, I own a Sony radio that came with my SL280 R129, however it only works with the tweeters. The issue persisted when I tested a different model of the same brand of radio. I have a build sheet from MB, and the car came with speakers but no radio when it was new. There are standard ISO connections in the dashboard, and there is a Sony 10 CD autochanger in the trunk mounted on a factory bracket; nonetheless, the same issue persists: there are no primary speakers. It has been suggested that a Becker amplifier, which is located beneath the passenger side of the back seat and appears to be in excellent working order when plugged in, could be the source of the issue. Is erasing this even possible? Because they are more modern and have features like bluetooth and aux, aftermarket radios are more than adequate for my purposes. Thanks for any advice or suggestions.

[Rojoires]

"How long is a piece of string?" in its purest form, I'm afraid. Who can say for sure what the 25–30 years of prior owners have done? A number of things could be wrong, including faulty or broken wiring, an amp channel that isn't working, or the radio's configuration.

Anyone competent enough to run a wiring loom directly from the head unit to the doors should also be able to figure out what's wrong with the current setup and implement the necessary bypass.

[Darrellll]

Two of the ISO connectors on my R129 are the standard 8-pole varieties (one for power and the other for speakers), and there's a third, 10-pole one that came from the memory that I assume supplied power to the optional amplifier—which, to be honest, isn't in my vehicle. Even though my car only has four wires connected to the 8-pole ISO speaker connector, the VIN decoder—which I have used a few times—suggests that it has rear speakers. In this thread you can find various images of these connectors.

There are two tweeters in the dash, a larger (bass) speaker, and a smaller (midrange) speaker on the R129 front doors. Being on my second R129, I can say that the original speakers are mediocre at best. I replaced them with JBL units of the same size in my previous vehicle and am planning to do the same in my current one.


The car's factory stereo was a Sony cassette player with a few shaky functions; I'm replacing it with a higher-quality CD player, which doesn't have any built-in amplifier. I plan to install my digital signal processor and multi-channel amplifier in the trunk, with the original speakers mounted on the sides of the back seats and a passive subwoofer on the luggage shelf—which forms when the back seats fold down—that can be easily removed if more room is required for luggage.

It seems like someone may have tampered with the wiring in your car, since the front door speakers and dash tweeters are connected in parallel. I'll be installing a 6-1/2" bass only unit in the lower door positions and 4" dual concentric units in the upper door position, also wired in parallel. My previous car had 5-1/2" dual concentrics in the rear, but this time I'll be using a 5-1/2" component system with the bass unit in the same spot and surface-mounted tweeters higher up for better sound dispersion. I'll post pictures of these in my thread once I have better lighting.

Typically, the speaker outputs on the main radio are where the Becker amplifiers are connected. When I acquired my W140, it was already equipped with the original Blaupunkt unit and a factory amplifier in the boot.

[QuirkEinstein]

I appreciate the responses. Based on what we can see, the vehicle is completely stock. My present SL and another were housed in a stable block by the former owner, a woman who owned a fleet of cars and used one every other year. A major dealer has always taken care of maintenance before that. Thanks to the car's long history of dry storage, the wiring and speakers are in excellent shape, and I haven't noticed any modifications to them. On one side of the center console is a dealer-fit Nokia phone cradle; it's well-made and matches the interior's right blue hue, so I plan to preserve it. After taking another look under the dashboard, I noticed a fused link for the phone along with its microphone and antenna wires. Additionally, there is a tiny multi-pin socket with two brown wires that connect to one terminal on the main harness. The radio's ISO ports and the Sony multichanger's connectors are also listed. It is possible that the multi-pin socket is to blame as it appears to be unplugged. The car's radio and CD player stopped working shortly after I picked it up from the auction; I subsequently discovered that the aerial had been detached and that the autochanger still had 10 CDs inside. If I can find a speaker output on the Becker amplifier, I may be able to short the two wires together using the multi-prong adapter. Given that I already have a spare radio, two Kenwood component speakers, and a variety of wiring and connectors, I don't see the need in going to any more lengths to acquire music. I keep the hard top in the rear of the garage, but I doubt I'll ever use it since I only use the car during the summer. The Alfa Romeo Spider, which I had been driving for a while but was finding increasingly difficult to enter and exit as I became older, was replaced by the SL. The Kenwood radio/CD/multichanger in the car worked fine; it appeared to be more user-friendly.

[AMG33D]

That kind of provenance, in my opinion, is meaningless in these kinds of cases.

A property developer was the only owner of the 129 we purchased in 2003; the property had a complete history. I uncovered the remains of two car phones and a radar detector concealed behind different panels of trim. It seems like they're the type of folks who simply bring their car to have x installed or removed without considering the process. If it functions properly, then it won't be noticed.
 

[Darrellll]

My only regret is that no one has ever tinkered with my wiring, and I hope it will never happen.

Even though I'll be installing extra cables for some of my gear and making my own unique ISO harness for the radio power, I will never cut or damage the car's original wiring.


After I install anything, it will be easy to remove it, so the automobile will remain unaltered. In order to install the loudspeakers, I only need to procure new trim panels to cover the areas on either side of the back seats.