so that video is an utter waste of time - it didn't fix anything - or indeed tell us anything we didn't already know

Hey guys any updates?
Basically , If i put this amp , I will use volume control , but if I am conencted to my aux source I can fully control the volume from my phone?

First of all I want to say **** Mercedes service. Why? To give a bit of context I replaced my w221 amplifier with a OEM one I got from ebay last year when the prices seemed reasonable ($500) so when my audio issue happened again I was a bit skeptic if it was the amplifier the problem or another piece mind you the radio part was replaced in the past 3 years also. So I did what any reasonable person would do and brought it to mercedes for a diagnosis (before bringing it I did my own diagnosis and always came with the error "open ring" which meant I couldn't detect which part was wrong) so I assumed they probably had a tool that or a way to find a way to see exactly which part was faulty. After 3 hours of waiting and 300$ they came out short and told me they couldn't find the issue because I have a aftermarket screen installed lmao they kept telling me on there computer it was open ring also. Fast forward a day later and I found this thread so I bought a fibre loop and did my own diagnosis and the issue was the amplifier which was a year old. Decided to go on ebay to find the exact one but **** was 1k so I went the hyundai route and bought this amplifier " 2013 Hyundai Genesis 5.0L Radio Amplifier ID 96370-3M360 OEM " it was plug and play and worked perfectly. Only issue that I recognized is the volume which can only be changed with pressing the mute button and I have noticed by bass is a bit louder but tbh its something I can live with for spending $200 to repair the issue. So thanks again to OP for recommending a hyundai amplifier.

FWIW the price on a new (reman) amplifier from Mercedes has come way down. I paid around $1500 for mine about a year ago. Now it's $857 from midatlanticmercedes. Seems pretty reasonable for a brand new genuine part with warranty. Good time to buy if you need one. 221-900-81-03-80

This thread saved me and my recently acquired 2009 CL550. I'm hoping to help any others experiencing similar issues with the Harman Kardon Becker amplifier.

After a TON of research, I decided to take a look at midatlanticmercedes as suggested by argon3030. The Harman Becker Amplifier is now on sale for $461! Though I didn't buy it directly from them, I did contact a friend who works for a MB dealership to confirm the part number. His dealership had the part in stock at a similar price!

The part number is 221-870-77-89-80 "Amplifier - Mercedes Benz" or "Remanufactured Amplifier 7021 For W221". I can confirm it was an exact plug and play match for the Model 7021 amp. It brought the COMAND system from visual navigation only to full AM/FM, CD, MP3, Voice Command, phone, etc.

There is an additional core charge, but all in for a part with a 1 year manufacturer warranty, I feel it's a great value.

Look online. Check with your local dealerships. Now may be a great time to buy a new amp!

two or so years back one regular forum contributor informed us - Merc had forced the OEM manu to make re-man units available sensible cost - as the stock one is such an unreliable bit of junk - seems few read his post ?

I think he went on to say its a used casing - with entire new internals

Did anyone find the fix for the volume knob issue?

Yes:
Turn the volume up or down.
Push the Mute.
Push the Mute again.
You are good to go, regardless of whether your car is moving or not.

Cheers

I know this is several years later, but yes, the Genesis amp is plug and play in the W221. You just have to mute and unmute after changing the volume. I still have the last two paperweights...I mean amps I pulled out of this car. The Hyundai amp was 140 bucks in November 2024, and the sound is just as good as the original.

after show your post i was very curious and I swapped my W221 amplifier with Genesis. It's worked but i have one problem with volume SCROL button. I was not able to control the volume strate, every time I had to change the volume and then press mute button then unmute.

Hey could you please contact me, I have the Hyundai AMP, and I dont have a sound and FM, TV AUX DAB is working without sound.

P.s. The Mute trick doesn't work.

AJ

yes, I noticed that post. Apparently used outside case with new internals. I'm seeing them for around $605 - $650 which includes a mandatory $80 core charge. A;so seeing them for $900-$1,100 at some dealer parts counters.

This seems a sensible solution... certainly miles better than a USED unit that at this point in time is minimum 11 years old, some 18 years old, which are at between $350 and $1,100 on EBAY....compared to new internals for $620.

before spending that money - unless its spare cash - testing a known used one to check yours is faulty is a sensible option - they are pretty much plug and play (as in any one should function - but subtleties might have been got at that can be played with using xentry)

we are still after a guinea pig to try programming the Hyundai amp with Merc software that operates minus its correctly functioning vol control - its clearly almost the same unit but can be bought for far less

Agreed. This is a rare MB part you can buy from the parts counter that seems almost 'normally' priced. While I wish it were brand new, this is the best option vs. paying almost as much for another old one bound for failure.

So I am at the point of ordering part 221-870-77-89-80, the remanufactured S550 amplifier. I am at this point b/c my second fiber optic loop arrived, same as the one I used last year to identify the Sirius unit needed replacing (which I did) and I put the new fiber optic loop into the connector for the Sirius FM module, and it does not fix the fact that my CD will load, but not play, and when I plug my iphone into AUX, doesn't see it. So my fiber optic testing loop from last year apparently still works fine.

2 questions:

1) I did check to see that the amplifier fan does not move. Is there any other way to make sure it is the amp that needs replacing and not some other module in the fiber ring?

2) Several dealerships and parts suppliers have this amp in stock. They all seem to have a 20% return charge, which I am fine with, but more importantly, they all seem to have the same language about "Electrical Parts are not returnable." Has anyone ever ordered one of these amps, then found out it wasn't the amp after all, but another module, and tried to return it for a refund -20%?

The sirius module is a stand-alone unit it has NOTHING to do with sound creation from any other audio source - if it dies it takes down the fibre loop and all things stop due to the break
On FM or AM radio (the Tuner that is also built inside the Amplifier for ALL audio) do you hear anything - if 100% normal the AMP is NOT the issue
The fan is a joke and that will help kill the Amp

I get no sound from Radio, b/c the comand screen says "device not available"
I get no sound from Disc b/c though I am able to load a disc, and the comand says it is reading Gracenote information, it stops there and nothing plays... so no sound from disc.
I get no sound from AUX, which is the last input in used (it has a dot next to the word AUX under Sound options) b/c the word AUX is greyed out... and when I plug my iphone into the AUX receptor as usual, there is no recognition, so no sound.

So bottom line, I get no sound from Radio, Disc, or AUX.

OK, I'm stuck and need specific instructions on how to determine my problem is the amp and not the Sirius module again. Reason is that I have found part 221-870-77-89-80. at several online parts retailers, but have verified with at least one that it is considered an electrical part, and electrical parts are not returnable. So I would be out $700 if I receive a remanufactured amp and it turns out my existing amp is just fine.

I used a fiber optic loop a year ago and dtermined that my audio except for FM radio returned to normal with the loop inserted in place of the Sirius module. This time, when I insert the fiber optic loop in place of the Sirius, the Disc player, and the AUX, along with the FM, continue to not work at all.

So that made me conclude the amp is the problem. Or the amp AND the Sirius.

Does any have a step by step set of procedures that I can follow to determine with certainty that the amp is not working? I mean instructions that a 10 year old could follow

yep take out the broken amp and replace it with a known working one - when all is normal - job done

well, I don't have a spare amp available to me. Went to a stereo shop, paid them $150 for a diagnosis, with the particular goal of identifying if my amp is bad, or not, since nobody here seems to know how to determine that.

The guy couldn't find anything, but get this, hired another guy to come see if the amp works, and that guy said the amp is fine. The stereo shop guy told me the fiber optic loop is intact... he shined light down somehow and determined the problem isn't in the loop.

So I'm back to square one.

NEVER expect anyone to be able to diagnose an issue with a merc - they main dealers with $12,000 kit struggle - so why should a hifi halfwit have any clue - most couldn't reliably tell you the time

OK, you appear to be saying that a car stereo shop can't do it, a dealer probably can't do it either, and the only way to diagnose is to start replacing (non-returnable $700) parts and see what works.

no I said find someone with a working amp and swap it over - diagnostics can't behave correctly if parts are physically dead

ANYONE pretending they are a decent Merc workshop will have one - and if they are any good, should be happy to stand there as you spend 3 minutes plugging it so he can laugh coz merc have been building cars like this for 20 years -

I have this issue with a 2007 CL550. I got a Hyundai amp for $85 and will pick it up Friday.

If I read right I should be able to change the volume by adjusting, then mute unmute

and nobody has the FM radio working with the Hyundai amp correct?