1997 W140 Coupe no sound from speakers

[S11YBM]

Hiya,

I need some help. I recently had some work done on the car and as part of that I asked the guy to remove the CD Changer. Since then the speakers don't work. I plugged the CD changer back in, but still no sound.

There is no amp in the boot (which I can see). Any ideas what could cause this?

Cheers
Shyam

 

[grober]

K6JRF Auto Page

My Mercedes S500 Coupe

www.k6jrf.com

K6JRF Auto Page

K6JRF Auto Page

My Mercedes S500 Coupe

www.k6jrf.com

 

[S11YBM]

Thanks, but nothing on there about no sound.

I plugged the CD Changer back again in and still nothing! I’ve tested each of the speakers and they all work. I tried a tape too incase there was an issue with the radio function.

 

[grober]

HAVE YOU CHECKED ALL THE FUSES

Mercedes-Benz S Class w140 (1997) - fuse box - Auto Genius

Mercedes S Class w140 (1997) - fuse box diagram

www.autogenius.info

 

[S11YBM]

HAVE YOU CHECKED ALL THE FUSES

Mercedes-Benz S Class w140 (1997) - fuse box - Auto Genius

Mercedes S Class w140 (1997) - fuse box diagram

www.autogenius.info

All fuses are fine, just double checked them.

The stereo works in another car, I tried another stereo in the CL and that doesn’t have sound either.

Are the speakers directly wired to the head unit?

 

[grober]

NORMALLY by this time the speakers will be driven from a separate amp-normally in the boot somewhere- the sound system should have its own data bus linking the Radio , CD PLAYER and AMP together. it may need resetting by powering all units down and powering back up again starting with the radio-----careful you may need the radio security code if its powered down completely.

 

[S11YBM]

NORMALLY by this time the speakers will be driven from a separate amp-normally in the boot somewhere- the sound system should have its own data bus linking the Radio , CD PLAYER and AMP together. it may need resetting by powering all units down and powering back up again starting with the radio-----careful you may need the radio security code if its powered down completely.

No signs of an amp in the boot. The connector on the head unit has all 4 speaker wires on there (see attached). I gave it all a reset by disconnecting the battery for some time.

 

[S11YBM]

I've found the attached documentation, it's confirmed that there is no amp.

 

[grober]

Radio stuck in mute mode. - MBWorld.org Forums

E-Class (W211) - Radio stuck in mute mode. - Hi all, I am new here. Just got my 06 E350 2 weeks ago. I love it. I am having a problem however. The radio is stuck in mute mode. The icon is in the display and no sound out of system. All other functions work fine. I have taken out the fuse in hopes...

mbworld.org

 

[S11YBM]

Radio stuck in mute mode. - MBWorld.org Forums

E-Class (W211) - Radio stuck in mute mode. - Hi all, I am new here. Just got my 06 E350 2 weeks ago. I love it. I am having a problem however. The radio is stuck in mute mode. The icon is in the display and no sound out of system. All other functions work fine. I have taken out the fuse in hopes...

mbworld.org

Thanks again for your help! My one doesn’t show the mute symbol and the stereo works fine when plugged in another car.

I’ve now disconnected the battery and will leave it over night.

 

[grober]

some options?

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[S11YBM]

some options?

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Those are all good options if the speakers worked

I tried a spare stereo in the car and that didn't work either. I'm trying to find the speaker wiring diagrams so I can trace them to check they're all fine.

 

[grober]

No signs of an amp in the boot. The connector on the head unit has all 4 speaker wires on there (see attached). I gave it all a reset by disconnecting the battery for some time.

WHAT are the voltages on pin 3 and pin7 with the radio on?

 

[grober]

W140 Speakers Go MUTE, Radio Still ON! Is this the start of many Electrical Problems. - PeachParts Mercedes-Benz Forum

1992 400SE. The radio works fine while in Key is in the ON position (vehicle off) or while idling, but as soon as you put it in gear, the speakers go

www.peachparts.com

The problem with all the older models as assumptions- assumptions that audio system is factory standard wiring and not aftermarket----- many of these modifications remain undocumented------- I suspect you may have sound amplifier system located/hidden somewhere in the car which may not be working or being switched on by the head unit. All you can do is start lifting carpets and removing trim in order to trace the wiring.

 

[S11YBM]

WHAT are the voltages on pin 3 and pin7 with the radio on?

Pin 3 (Telephone Muting) - 3.97
Pin 7 (Switched Positive) - 12ish

I think you're right, I'll need to trace the wires. It's doing my head in! Did a battery test with the speakers and all respond. I connected another stereo with an adapter which uses the bare minimum connections (omits things like Speed Dependent Volume and Telephone muting) even that had zero sound.