Hello, just wondering if anyone has removed the B&O Amplifier before from the Trunk. I’ve been having a very annoying issue with my sound system lately to where if I play music too loud or The bass is too strong my Audio will cut out and almost sounds like it’ll go into a safe mode. This will only happen when the music is too loud or the bass hits hard. This problem first started to happen on a very hot day where I was blasting music and bass was around 5+. Ever since then whenever I play the music too high or the bass is too strong it’ll cut out. For it not to cut out I can’t keep the bass high or play the music loud. I took it to my Mercedes’ specialist and he checked for any updates or codes and the only code to pop up was an overheating code from the amp. He checked the AMP itself with his computer and it seemed to read ok and only issue was the overheating code. Anyone got any recommendations? Or has anyone encountered this issue? Thank you! Any info will be helpful! Below is what I think to be the main amplifier, if not let me know where it would be. Picture taken is on the left side of the trunk!

exposed heatsink
​​​​​​This does look like the main amplifier, tucked behind the suspension air tank
While you are busy taking everything apart... look for any clues of damage... water intrusion, colision, dust ball in the vent...

All my B&O Amps were in the shelf at the top of the trunk

large heatsink amp
My mistake... on the tank left side of air tank is the satellite receiver and on the right side is N40/3 amplifier. (small N40/9 amp being on trunk top)

do you know if the N40/3 is mated to my B&O sound system or the N40/3 is mated to the Harmon kardan sound system only?

I couldn't tell the difference based on options codes only, N40 is the amp designation parts family.
Now you can further invest your time all you want to research VIN information
-Or you can have a quick look around your cargo area and post pictures

What do you mean by shelf at the top of the trunk, picture provided if possible?

Glad to see you back buddy, where have you been?

This problem is OVERHEATING protection...

I can help you look for evidence with your B&O unit. Show us pictures of both sides of circuit board and we'll go from there.

-- Thermal paste may be an issue if it's running down vertically...

-- Unmachined heatsink surfaces may be involved with poor heat conduction...

-- Exploded capacitors may be at play...

This is going to be very interesting, first step is to find where exactly the amp units are located, second step is to see which one is the issue then third step is the interesting part.

let's put our thinking cap on to make a good guess...
To figure which unit overheats: crank up your music to the point where amp usually cuts off - Feel both unit for high heat, disassemble the hotest one first ✌️

That’s the plan! Thanks for the help so far

Still here, just going through the most frustrating car buying search ever LOL


Yeah there is a shelf at the top of your trunk that often contains the comfort box, but on the B&O cars it has all your amps

That is very helpful thank you, one less of a step to worry about

By any chance do you know what amp does what? And possibly the voltage of the amps?

Left side unit looks like pre-Amp/DSP section, right side looks like the power amp final stage: that is the one getting hot right??

These amplifiers look pretty small, no tandem unit located near the air tank??

I am going to a mechanic shop in a little bit to try to tackle this issue today, I haven’t checked to see which one is getting hot yet. I will check right now to see if there’s anything on the right of the air tank!

Here's the WIS document for the amps for the B&O system, in case that helps. At the very least, it confirms that both amps are in the tray and helps identify which is which.

Hello Log that does help a lot, since the N40/3 seems to be the main unit I would think thats the one causing the issue but not completely sure.

There is some sort of black box with wires on the right of the tank but after seeing the diagram Log sent I believe the amps on top of the trunk are the only amps we should be looking at and possibly the only amps in the vehicle for the sound system according to the diagram

I believe you're correct on those being the only amps. I thought I had read something about amps under the front seat, but it could have been a different component since that was in a thread about retrofitting the newer COMAND. I've attached the documents for the standard sound system here for reference. I also found a document that shows an amp (N40/9) down by the spare tire, but it's just a generic function description that applies to several other vehicles.

As for which amp is causing the problem, that may be more difficult to figure out. If the error code gave more detail, that would be your best bet. If the problem is from lack of heat transfer to the heatsink, the problem amp could potentially feel cooler to the touch.

For the code it was a overheating code, wasn’t told which amp it was or the code # but I was told it was a overheating code that popped up and was also told my amps are reading that they’re good. Woudlnt the problematic amp be a lil hotter to the touch since it’s a overheating code?

That depends on how the temperature is read. It's probably reading ambient temp from somewhere inside the amp or from the heatsink, which would mean the amp would feel hotter to the touch. On the other hand, it's possible that they're using some fancy chips for the amplification that are capable of directly reporting temp. That would mean the chips could report overheating without transferring as much heat out through the heatsink. I don't know enough about the electronics in these amps to say for sure either way, I'm just used to dealing with other devices where the latter case is more likely.

Something came up so I’m just going to go to the shop tomorrow. If you had to say what the issue would be what would you say? It could possibly be the thermal paste or a soldering issue what I’m thinking

Based on the symptoms and what others have said, I'd say the thermal paste in the main amp is a good possibility. It should at least be fairly easy to check. If either of the amps do end up coming apart, get some pics of the inside. I haven't been able to find much info on them.



The above is a screenshot of xentry from the main amp in my car, the shop should be able to read those temp values. I believe the first one is in a different module, but it has the same notes for temp cutoffs. For reference, my "inside control unit" temp was rising fairly quickly with the system muted, just sitting in the garage with an ambient temp a bit over 90F.