doctormdds

My car is a 2007 SL 550. The radio/CD player/Navigation all appear to function normally but I have no sound. Does anyone have an answer to this? Thank you!

diablo2112

Other than the obvious (mute button? Fuse for the amplifier?)....

Sound is provided over the MOST fiber optic bus to an amplifier in the side panel behind the drivers seat. If there's an break in the MOST fiber optic loop, you won't get sound. There's roughly a half-dozen devices in the loop, and any one of them could have an issue.

This is a harder problem to track down than you may want to hear. Read up on the MOST fiber loop, and if you can find a bypass plug, you can check each component in the loop to see if it's the problem. Sorry you're having this problem; audio/COMAND in the R230 is the single biggest complaint/issue with an otherwise fine platform (well, there's the ABC system....)

seven_out

Since the navigation functions, you know that the MOST fiber optic network is fine; the fact that the radio functions suggests that the audio gateway module is fine as well. This leaves the audio amplifier as the most likely cause of your problem, I believe.

A Star Diagnosis (SDS) computer can check for faults in the amplifier and execute steps to troubleshoot all of the components. I suggest taking the car to an independent shop equipped with SDS, or better still, purchase an SDS of your own from eBay or alibaba.com. One can be had for as little as around $300.

diablo2112

Good points, Rod. Nav does send info to the dash computer over MOST. Probably not the fiber loop.

IanRC

Hi, I had the same problem - turned out to be the fuse by the amp under the CD changer behind the passenger seat (RHD). Just remove / lift up the storage box (held in place by a few torx bolts) and the fuse is under the box.

doctormdds

Thank you all for giving me some direction on where to start. While I'm mechanically inclined, electrical issues are not my thing. I'll let you know what happens. By the way, I've already had issues with the ABC system. I've had a ruptured hose replaced and I've had the ABC pump replaced. Fortunately, the car was still under warranty at that time. Now, I'm on my own!

seven_out

This is why you want a Star Diagnosis computer if you wish to save money and troubleshoot this problem yourself. Its menu-driven software guides you through the troubleshooting process. In a sense it's analogous to using Turbo Tax to generate a tax return, or Legal Zoom to generate a legal document.

A 13-year-old with a Star Diagnosis computer in his hands would likely have an easier time troubleshooting your problem than a Ph.D with a doctorate in electrical engineering who lacks SDS.

aschueler831

My fiance changed the electronics battery in my SL500. After reconnecting, we found no sound, no CD changer, no satellite, no extra sound options.

After reading the posts in this thread (thank you for the posts), we went to work. Below is a little more information.

Found the fuse box behind the passenger seat, under the storage box.

Fiance had to remove the side panel and loosen the back panel to get the storage box out. After removing the side panel, the back panel going across the back has to be loosened. Fiance removed the two passenger side, back panel torque screws (hidden by the side panel). This allowed enough flexibility in the back panel to be pulled forward. There are two torque screws behind the storage box as well (note the little holes for a screwdriver to fit through). Loosen the two torque screws, but not completely, otherwise they will fall into the wires and electronics under the storage box (which happened to us). Otherwise you risk breaking either the storage box or back panel. BTW, this is essentially the only way to re-install the storage box. You can then lift the storage box out of the compartment. Fuses exposed.

The radio fuses are 57 and 77. However, after pulling and seeing they were not blown, fiance pulled almost all the fuses. He then told me to check the radio again. Yahoo! All (Volume restored, CD was recognized and Sirius XM was working) was back to normal. Hope this additional info helps.

next2pool

You should be able to lift the bottom out of the storage box and access the fuses directly without removing the box itself.

Wardsweb

I had the same issue yesterday with no sound. Everything functioned but no sound. I don't know if it was an intermittent connection or a software glitch but it started working again within a few hours. Maybe the recent cold snap had something to do with it, as after the car warmed up, it worked. No issues today.

Jason Floerke

I have had a problem with my sound for the last couple years. When it is below 50 degrees outside there is no audio, however head unit, cd player, nav all works. I think the problem is the amp but unsure. I'd like to install aftermarket amp if that is the problem, is the amp connected through the MOST?

pmercury

iTrader: (2)

Ebay amps are cheap
if you pm me your VIN number I can list the compatible OEM amps part numbers
I do not suggest to replace Command by Chinese radios as you will never achieve great sound unless you buy a 1000$ quality 5 channel amp like I did + a lot of cable work (if you are on MOST system)
another option is to buy a quality radio like Clarion or so + lots of cable work (if you are on MOST system)
If you are lucky and your car is on D2B things are easier as you can buy a D2B converter box

Dudeman

Can you please expand on that last comment about the D2B converter?

I've done a complete Command replacement for my SL550, which has a MOST interface, and I can tell you that replacing the head unit is not that hard, and you can maintain your original BOSE or HK amp. There are analog audio to MOST interfaces available from a few vendors, and they certainly keep the wiring to a minimum.

On the other hand, there are no analog to D2B converters that I know of, so I don't think those are the "lucky" folks, as in their case, a complete replacement of the existing system is required. And that is where the "lots of cable work" comes in.

pmercury

iTrader: (2)

my fault, so it's the opposite
no analog to D2B

sorry, I worked on this 2 years ago







__________________________________________________ __________________________________________________
There are many choices for DAS/Xentry Diagnostics for MB.
Ensure you have the right information before getting one. There is too much misleading info.
I’m a forum member and programmer who’s learned the hard way. PM me if you have any questions.

bobterry99

An '05 car has MOST, and for that AVIN makes a converter.

With an analog-to-MOST converter any head unit should provide the same sound quality as the original COMAND.

doctormdds

The reason I had no sound whatsoever is because the amp was defective. The MB dealer allowed me to purchase a used one on eBay and they installed it for me. That was much less expensive than buying anew one.

BenzNinja

iTrader: (4)

Lucky you but a simple advanced Xentry diagnoistics would have told you that within a minute.
The dealer money would have paid for the entire system and membership
click my banner

doctormdds

When I had this done the service writer, Harrison, was a really good guy. They had given me a loaner while they were checking my car. Harrison called me and said the amp was bad in my car. When I asked about cost to repair, he told me "You're probably going to want to go to eBay for this one". I bought a used amp from eBay for $300. The dealership charged me $250 to install it. So, I had sound again for $550. Unfortunately, Harrison is no longer at the dealership.

BenzNinja

iTrader: (4)

thats a great deal