In a 2001 Mercedes-Benz SLK, the horn relay is typically located in the fuse box. The fuse box is usually found in the engine compartment, near the battery. You can refer to the owner's manual for a detailed diagram to identify the specific location of the horn relay within the fuse box.
A 002 820 62 89 oem (mb)
I have a 2003 MB S430 and its $10,000......
there is a set screw in the base of the mirror loosen then slide up
in the relay box next to the fuse box underneath the hood
buy it used from eBay or junk yard, no a days is cheaper to buy it through the internet .
with a fine blade or knife, prise open the key fob from the back. Remove the two batteries inside and replace with new ones. The fob will snap back into place after
Bring to dealer for repair
The recommended oil for a 2006 Mercedes SLK 350 is a synthetic motor oil with a viscosity of 5W-30 or 0W-40 that meets the MB 229.5 specification. It's important to use high-quality oil to ensure optimal engine performance and protection. Always refer to the vehicle's owner manual for any specific recommendations or requirements.
http://www.installuniversity.com/mb/w203/w203/fp.html
Its probably a fuse, there are 2 fuse boxes. one is under the hood on the drivers side towards the rear, and the other if inside, once you open the drivers door on the left side of the dash, (only visible with drivers door open) I have seen a horn go back and blow the fuse, so make sure to check amp flow before replacing the fuse.
Take your car to MB dealer and they will reset it for you ....simple I think the person was wondering how you reset the check engine light yourself. Obviously, everything can be fixed by taking it to a MB dealer. I imagine that is not at all what they were looking for. All you have to do is to pull the EFI fuse and then put it back in. This will reset the system. That is much more simple.
Your compressor relay,or fuse or the pump has gone bad. First check fuse right side 40 amp fuse ,replace if blows the fuse,check relay off market price is 32 dolars compare to MB price 75 dollars, if both replaced then rep[lace air compressor.