BOTUS

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

acmw

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?

AKZ

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.

argon3030

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

AlohaBenz007

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!

BOTUS

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

S550TK

Did anyone find the fix for the volume knob issue?

houmem24

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