[MaxwellAlan]

I recently purchased a '94 Mercedes E320 wagon and it is having issues with the output in the left speakers only. The right speakers sound perfectly normal but only the left rear speaker produces sound and it is distorted or blown.

When I reverse (what I believe are) the two stereo output channels from the back of the deck/head the right and left outputs show the same symptoms on the left speakers and same on the right. My deduction from this is that the problem is either with the left power amp channel, the speakers, or the wiring/connections between them... If so how easy is it to access these for troubleshooting? And are there any other thoughts as to what I can look for?

Are there any wiring diagrams or schematics available for these sound systems? Or service manuals for how to access the wiring?

...I have experience troubleshooting and servicing guitar amplifiers and am proficient with a multi-meter and soldering iron. It is also worth noting that I am aware of the risks that one undertakes when working with electrical equipment and understand how to discharge a circuit properly if I do need to work on the amplifier.

 

[macdrone]

Fader

Mine has that issue but it's the fader dial becoming corroded and dirty. You may not have one, I covered mine up with a 1995 center wood and have to take it part to mess with it every so often.

 

[Jayare]

I would suggest contacting Becker in NJ and have them referb the head unit. Use the search function for their contact particulars.

Good luck

 

[Clarkz71]

When I reverse (what I believe are) the two stereo output channels from the back of the deck/head the right and left outputs show the same symptoms on the left speakers and same on the right. My deduction from this is that the problem is either with the left power amp channel, the speakers, or the wiring/connections between them... If so how easy is it to access these for troubleshooting? And are there any other thoughts as to what I can look for?

A 94 head unit has 3 multi pin plugs at the rear, how are you switching channels.

The early radios did have separate speaker outputs.

 

[MaxwellAlan]

1) "Mine has that issue but it's the fader dial becoming corroded and dirty. You may not have one, I covered mine up with a 1995 center wood and have to take it part to mess with it every so often."

-The faders on mine have digital -/+ buttons that pan the speakers. The panning function works perfectly fine.


2) I would suggest contacting Becker in NJ and have them referb the head unit. Use the search function for their contact particulars.

-Thanks for the referral but I will be fixing this myself unless I get stumped. I'm fairly certain that the head unit is working properly but if you have any reason to believe otherwise please let me know.


3) A 94 head unit has 3 multi pin plugs at the rear, how are you switching channels.

-Correct. The plugs that I reversed were after the 3 plugs that come off the head. There were two circular/spherical plugs that were identical after these three plugs. I flipped them around figuring that they are likely the outputs and I'm pretty sure that it reversed the channels... I'll double check with audio that I know has a hard stereo pan and get back to you but I'm 90% certain these switched the channels.

 

[LasCondes]

Hey MaxwellAllen, have you figured out what the problem is with the sound on L speakers? I have the same issue. At times, I will pump the volume up, real high, and I get to work, but not for too long. I also get occasional static, that has nothing to do with antenna reception.

 

[macdrone]

Capacitors failing in the amps in the trunk? Corrosion on connections? That trunk retains moisture pretty well especially when the trunk seal is cracked and shrinking.

 

[Clarkz71]

Can we assume you have tried the balance/fader
adjustment at the head unit?

Sent from AutoGuide.com Free App

 

[LasCondes]

I have tried to play with my digital balance/fader, but to no avail. "Macdrone" says the moisture could have something to do with it. Last year I had major moisture in my car as I parked it outside and the trunk seal was nearly gone. I have since gotten me a new trunk seal and I now park inside, Maybe I'll look to get me a new amp.

 

[LasCondes]

OK, I got me a new amplifier and installed it this morning, an aftermarket called DHD 2004, an exact replacement to the the one I took out, which I have had for the last 8 years. The bad news is that the left side continues NOT to work. I should clarify that left rear speaker does work, however, door and dash speakers do not. I checked the plug that goes into the radio and all seemed normal. I'm now so confused

Any other ideas out there??

 

[bmwpowere36m3]

OK, I got me a new amplifier and installed it this morning, an aftermarket called DHD 2004, an exact replacement to the the one I took out, which I have had for the last 8 years. The bad news is that the left side continues NOT to work. I should clarify that left rear speaker does work, however, door and dash speakers do not. I checked the plug that goes into the radio and all seemed normal. I'm now so confused

Any other ideas out there??

Can you to fade the signal front-rear and left-right via the HU? And does it track correctly with the adjustments, i.e. you fade rear and only the rear speakers play?

Your car doesn't have an original amplifier, correct? Is it a plug and play to the original or is it a typical aftermarket unit (has individual screw terminals)? In the original (MB) stereo config, the dash and rear door/parcel speakers are driven off the HU. The front door speakers are driven by an amp whose signal comes from the dash speakers (dual voice coil) and not directly off the HU.

I would start with the HU. Get a schematic for the radio, trace the wires back to those circular plugs you mention (if that’s where the speaker signals go) and disconnect them. Now you have two options: First, use a DVM or scope (set to VAC/AC coupling), probes go to speaker +/ - and measure the output for each speaker individually. You should get a couple of volts (the amplitude will go up and down) with the HU volume turned up and playing something. Second, you can hook up a known working speaker (2-8 ohm) and test for output (bypassing the amplifier and wiring from the amp to the speakers).

 

[thesameguy]

The factory stereo has four channels out (LF, RF, LR, RR) via speaker level signals that travel to two amps in the trunk, right hand side near the hinge. One amp receives the LF, LR and the other amp the RF, RR. One amp handles the left side of the car, the other amp the right side of the car. The amps internally send full-range signals to the rear speakers but break up the signals to the front speakers sending highs to the dash speakers and lows to the door speakers.

The amps are identical, so I would start by swapping the connectors to them and see if that brings your speakers on the misbehaving side back. If not, it's not the amp.

You can also unplug the connectors from the amps and use jumper leads to connect test speakers directly to the head unit, bypassing the amps entirely. The wiring on the amps is fairly obvious - look for two pair of small-gauge wiring in similar colors (ie. blue, and blue with stripe). They will match the wires coming out out of the B (middle) connector on the back of the head unit. Connect a speaker to each of the matching pair of wires. That will tell you whether the signal from the head unit is there to drive the amp in the first place. No sound = no signal = faulty head unit.

Testing the speakers themselves is slightly more cumbersome, since it requires real dismantling. I'd start with these two tests and see where you get. My gut tells me you have a faulty head unit.

 

[bmwpowere36m3]

The factory stereo has four channels out (LF, RF, LR, RR) via speaker level signals that travel to two amps in the trunk, right hand side near the hinge. One amp receives the LF, LR and the other amp the RF, RR. One amp handles the left side of the car, the other amp the right side of the car. The amps internally send full-range signals to the rear speakers but break up the signals to the front speakers sending highs to the dash speakers and lows to the door speakers.

The amps are identical, so I would start by swapping the connectors to them and see if that brings your speakers on the misbehaving side back. If not, it's not the amp.

You can also unplug the connectors from the amps and use jumper leads to connect test speakers directly to the head unit, bypassing the amps entirely. The wiring on the amps is fairly obvious - look for two pair of small-gauge wiring in similar colors (ie. blue, and blue with stripe). They will match the wires coming out out of the B (middle) connector on the back of the head unit. Connect a speaker to each of the matching pair of wires. That will tell you whether the signal from the head unit is there to drive the amp in the first place. No sound = no signal = faulty head unit.

Testing the speakers themselves is slightly more cumbersome, since it requires real dismantling. I'd start with these two tests and see where you get. My gut tells me you have a faulty head unit.

My '95 E320 wagon has 1 amp and it only drives the front door woofers (Radio MB with Active-Bass-Speaker System) and it standard on E320 as of MY94. The one you mention is standard on 400E/500E and optional on others (Radio MB with Sound System).

 

[valensf]

We're you able to find the causes?? I am having the same problem.

 

[LeftCoastGeek]

We're you able to find the causes?? I am having the same problem.

that was 2-3 years ago.

given the 3 W124's I have, all of which came with 'active bass' not 'sound system', the common audio problems are...

A) fader fader fader. remove fader, clean pot surfaces with DeOxit. (later cars don't have a fader)

B) speaker cones crumbling due to age, especially dash speakers

C) stereo itself, but that will affect both speakers on the same side (actually, that depends on the year car)


if you install an aftermarket stereo, you need to bypass the fader and find the actual individual speaker wires, as the factory system has common ground, which no modern stereo will tolerate. if you do this correctly, the active bass in the front doors will continue to work as the AB amp is wired to the front speakers. I found with a pioneer that using about 3dB of bass boost helps the active bass balance out.

if your car is one of the ones with the 2-piece radio, then stereo install is more involved, as all 4 speakers are wired back to the trunk where the radio deck is, the thing in the dash is just a control unit.

finding the right size 120mm dash speakers in the USA is nearly impossible. you have a few choices, find some $$$ Rainbow 100's from .EU for dropin installation, the inexpensive but really quite decent CarPower CRB-120PP are an exact fit, or hog out the dashboard to squeeze a pair of 5.25" speakers in (the stock speakers are about 4.75"). a complication with larger speakers is the magnet will probably run into the frame crossbrace under the windsheild and cutting this could impact the structural integrity of your car.

 

[Real1shepherd]

If the voice coil & spiders are not shot, often paper type speakers can be re-coated and they take off sounding like new....providing they have sound surrounds(car speakers usually have a good surround material, versus home speakers of this vintage). The paper is coated with a glue that you buy when you're replacing foam surrounds in home speakers.....you just dilute it with water a bit so it brushes on thinly & easily.

Kevin

 

[LeftCoastGeek]

yeah, 3 out of 3 of my W124's had front dash speakers with splits/cracks in the cones around the edges where they flex.

 

[bmwpowere36m3]

Most W124 speakers I've seen, it's the rubber or foam surround that deteriorates…. I already replaced one dash speaker with another from a parts car and the rears (wagon) I bought Blaupunkt 3 or 4" speakers for less than $50. Not worth re-gluing the surrounds IMHO since the paper cones likely will deteriorate with time as well.

 

[LeftCoastGeek]

the rears in a sedan or coupe are 140mm, which is pretty close to 5.25" (its actually 5.5"), its the 120mm (4.7") fronts that aren't easy to match.

 

[valensf]

Thanks, Guys for very informative advices. As the original poster, cleaning the fader did fix it but temporary.... Is replacing fader switch good idea then??