HoustonYank

Just bought a 2007 550SL (59K miles) at Mecum. Take it home and find the radio has no sound. I tried a CD in the dash changer and that now won't eject. The comand screen shows the radio station as well as changes when I make them, and in CD mode circuits through the tracks, but no sound. I started the car a few hours later and the sound worked. The next day, no sound again. I shut it down, waited and restarted it, but no sound. Navigation does work. Don't even have title yet so I can't drive it anywhere. Not sure where to begin diagnosing the problem. I'm not very mechanical. Thanks for any advice. (Incidentally, if I decide to keep the car, I will need to figure out how to get Bluetooth streaming and Iphone connection.I currently have a '13 350SL and am spoiled by "modern" technology.)

Alan Gauthier

Periodically I have had the same problem. My car sits for extended periods and sometimes when I start it it takes a long time for the sound to come on. The display shows station and everything seems fine except not sound. I have found the porblem to be the state of battery sharge. Putting a charger on the supply battery and bringing the battery to full charge has fixed my problem everytime. I shoulld note that my supply battery is new but not driving the car frequently causes the battery to drain. I had this situation last week and the battery showed 77% charge and the radio would not come on until I charged the battery. Hope this is your problem as well.

HoustonYank

Seems like a lot of effort for a car that supposed to be so well engineered. Thanks. I will check that out. Are we talking about the battery in the trunk?

HoustonYank

UPDATE: I bought a Foxwell NT710. Plugged it in and ran a scan. OK. Radio not working. But here’s the punchline. I wait a couple of days, no radio, and drive the car around the neighborhood. Park in my garage and plug the NT710 in and as soon as I do, my radio starts working!!! What is going on?

sivikvtec

Sound is controlled by the audio gateway and amplifier mounted underneath the storage box with the cd changer.

Possibilities I can think of:

malfunctioning amplifier

malfunctioning audio gateway

malfunctioning device elsewhere in the system that is sending a mute signal to the audio gateway

HoustonYank

This has been my impression. It’s as if everything is functioning, except it’s on mute. I’m not capable of handling this kind of work myself. Where do I take the car to get it repaired without it costing a fortune? I can see the repair costing as much as installing a new module.

sivikvtec

It looks like the mute wire going into the audio gateway is grey/green, part of the four pin connector that is integrated with the orange fiber optic connection:

https://mbworld.org/forums/attachmen...ntrol-unit.pdf

you could disconnect that wire first and see what happens.

HoustonYank

I bought the Foxwell NT710 and ran a diagnostic on the '07 550SL. Still have sound occasionally...but mostly not. The only relevant hit I got was an AGW-Audio Gateway (Most network management, diagnosis gateway, radio tuner) that had a pass/no fault, but when going under live test to activate the most it claims the battery is low. Yet, the charge on the battery is over 12.4. No other faults. I got a bid to install a Kenwood 807 and bypass my amp, for $2000. Another for a Kenwood DMX 5020S for $1100, assuming I don't need a new amplifier. If I do, then another $400. He did not recommend bypassing the amp. What to do?????

A1EK

I have had issue with no sound for about a year, its very common as others have also mentioned this fault.
If you car Comand has all the functions showing still i.e. Radio stations, telephone, navigation and does not show 'system unavailable' which shuts off after 15 seconds, I would surmise the amplifier is bad. if the audio gateway is bad then it usually shuts the system down with the error message.
I by-passed my amp when I was trouble shooting using the fibre optic loop, and I had the everything working, apart from obviously no sound. If you have the amp without the fan, they are cheaper and you can get them on ebay. If you have the amp with fan and grey connection (not green) they are more expensive.
This may help you.

HoustonYank

Brought the ‘07 550sl to a car audio shop. After two hours of diagnostics, no definitive solution to the issue with the sound. They felt it’s a 50/50 shot it’s either the head unit or the amp and the OEM amp, installed would be $750-then I’m back to square one with no Bluetooth. His recommendation was bypass the amp, get a Kenwood DMX5020S with another amp and bypass the original amp. That, plus a camera would be $1500 plus tax. So, folks, that is what I’m going with. Installation tomorrow.
Wish me luck! Thanks. Dennis

HoustonYank

I replaced the Comand with a Kenwood 5020S. Also replaced the amp with a Hiphonics 5 channel. The Car audio shop said the Bose subwoofer had such a low ohm rating, the replacement amp was too powerful for it. They were going to instal a large SW in the trunk but preferred to take it to test sound for a couple of days and it is a bit “tinny.” I made some adjustments with the fader, moving more sound to the door speakers and adjusted EQ, but still lacks bass. Any thoughts on EQ adjustments and crossover settings would be greatly appreciated as It’s Greek to me. I bought a Rockville SS8P 400 watt low profile SW which I hope arrives in a week. Not sure whether to have it installed in trunk or under seat. Hope it solves the issue. Any suggestions very welcomed. BTW, the CarPlay works great!