vipsa

So my horn doesn't work anymore. I looked at the fuses in the fusebox under the hood and they're all good.
I took off the airbag and made sure the plugs are nice and tight.
I went in and made sure the connectors on the actual horn behind the passenger foglight are on good and they are.
I'm out of ideas now. The weirdest thing is that on the first startup of the day, if I press the horn, it will very faintly beep for a split second and then nothing.
Now does the alarm beep use the horn or does it have it's own separate siren? The locking and unlocking beep works fine.

Anything else I can try next? Anyone know how to test the horn by bridging the fuses? How about taking it off? Does the whole bumper need to come off?

xXHotelCrazyXx

Horn relay or horn

vipsa

Where's the relay? The only thing I found was the two "fanfare" fuses in the fuse box.

vipsa

Ok, I found the relay. It's right above the horn fuse 31 (fanfare) in the fusebox. Here's a picture of it. It is clicking and I swapped it with the other relay in the fusebox that has the same part number, so the relay is not the culprit. Next up is checking power at the horn. Are there two horns or just the one behind the passenger foglight?
Also, anyway to get to it without removing the bumper?

xXHotelCrazyXx

I believe there is one horn. Check the connections on the horn and make sure they aren't corroded. Sounds like the horn is bad.

vipsa

Ok, I pulled out the horn by the passenger side fog light (LOW tone). Tested it by giving it 12v directly and it seems like it's out. I found the second horn (HIGH tone) by the driver side fog light but that one is really hard to pull out, so I couldn't test that one out. Anyone know if both horns are wired sequentially and when the LOW one is out, both won't make a sound?

xXHotelCrazyXx

It is unlikely that both horns would fail at the same time.
You may not have realized that one horn had been bad for a while. When you heard the horn honk, it made you think all was well under the hood. When the second horn failed, it was time to do something. While this is rare, it can and does happen. You may have to just replace both horns to fix the problem.

SoCal208

Thank you for this thread, since I bought the car (2008C350), the horn is only in low tone. After reading the thread, I check fuse # 31, it was test & it's good, but in the wrong position in the fuse box, I reseat the fuse as it should be, voila !, the horn sound good (low & high) as it should be !. Thanks VIPSA for the picture of the fuses !.

vipsa

Glad this helped you. What do you mean the fuse was in the wrong position though?

SoCal208

The fuse was NOT line up like the other fuses, but it was off to the left side of the fuses box. After testing the fuse (be sure it good), I re-install the fuse (the way it should be). It work for me. Again, thanks.

vipsa

Just to give an update. HotelCrazy was right, it looks like I already had a horn out when I bought the car and now the other one went out. I went ahead and ordered a set of PIAA 500Hz/600Hz 115db horns. They came in yesterday and I replaced the Low tone one by the passenger fog light without a problem. They're plug and play basically.
No rewiring needed and it bolted on to the stock bolt location.
The driver side HIGH tone horn is going to be a ***** to replace. I will be removing the tire and wheel liner, to get the washer fluid reservoir out of the way to be able to replace that horn.
But it looks like the issue is resolved. Hope this thread helps someone else that encounters this issue.

BTW the PIAA horns sell for about $46 on Amazon for the set. The crappy Bosch OEM horns are going for close the $60 each used. So not only are the PIAAs much louder and better sounding they're much much cheaper and like I said plug and play.

angeloxnet

I have the exact same issue, in fact I remember the day when my first horn died, and when my 2nd horn went, the last "hoorah" slowly faded away. No I have no horn, I verified fuses and relays as well.

Is it normal for our horns to be dying? Do I really use them that much? lol

vipsa

It looks like the bosch oem ones are pretty crappy since I've seen quite a few posts for horn replacements. Also the amount of them that sold on eBay is unusually high.

cmarilee

Today while I was driving and on the phone (bluetooth), all of a sudden I heard a loud noise - I thought someone was honking at me but i realized it was my horn - it went on for about a minute or two and then stopped. I don't know if it had to do with the phone or what (the phone still works). Then, when I tried the horn, it doesn't work at all. I plan to take to dealer tomorrow because I assume it's under warranty, but also have another question. When I bought the car about 6 months ago, I found out from Mercedes (NOT from the dealer) that when the car was about a year old, the sunroof motor was replaced and the headliner removed and reinstalled. The funny thing was that at that time, the car reverted from individual ownership to the ownership of the dealer and it was used as a loaner car for the next two years before I bought it from another dealer. The dealer who owned it originally told me the sunroof motor was a warranty repair and it was necessary to remove the headliner to repair the wiring. A friend told me that airbag deployment can also damage the sunroof motor and possibly the car was in an accident but the dealer may have fixed it and then used in fleet of loaners. Is this plausible? How would someone know if the airbag ever deployed or the car was in an accident? Is that not possible to know once the airbag has been re-installed? I was thinking maybe the horn is a related problem??? Another thing is the car seems very noisy from wind/air - much more than a Mercedes should be. I can't find any air blowing in but even passengers have noticed that it feels like we're in a windstorm anytime over about 60 miles an hour. Is this normal? I appreciate any thoughts.

rookiezxc

I would bring it to another benz dealer and check for any body damage or any past accident damage.

cmarilee

Thanks. I took to a different dealer today - they diagnosed and have to replace the entire steering wheel and column, etc. - I guess the horn and airbag and all kinds of wires are connected together. I'm asking them to do a road test to gauge the noise of the car. They loaned me a brand new C300 and it is as quiet as could be compared to my car, which sounds like I'm driving into a storm when I'm driving failry fast. I get bad karma from this car.

anthony1991

Hi. I was wondering if you could possibly help me. I have a 2008 Mercedes Benz c280 with fuse box w204. I have discovered my fog lights are not working so I put in new globes but they still don't work. The next thing I was going to try was put a new fuse but I realized after taking the cover off there was no diagram to tell me which fuse was what. Does anyone know which fuse it is for the fog lights at all?

anthony1991

Hi. I was wondering if you could possibly help me. I have a 2008 Mercedes Benz c280 with fuse box w204. I have discovered my fog lights are not working so I put in new globes but they still don't work. The next thing I was going to try was put a new fuse but I realized after taking the cover off there was no diagram to tell me which fuse was what. Does anyone know which fuse it is for the fog lights at all?

AndreK

Hi, can anyone tell me, i bought a car and the airbag came out. The controls and horn on the steering is not functioning. I replace the airbag with a new airbag. Plug the wires green, yellow and black in properly. Still not functioning. It show on the dash "ESP faulty, drive to workshop" and "restrain system not functioning drive to workshop". I took it for dianostics to be reset. They cleared all the faults and still show the same and still volume and horn on steering not functioning. Its a C230 compressor coupe 2005. Is there anyone who can help me please?

Josh.A.Hussey

I am sure their are plenty of people who can help, but you should post in the W203 section.