SLK R172 - Hazard fuse keeps blowing plus smoke!

[PaulVarney]

Hi, I have exactly the same problem with my 2012 SLK. The first sign was the warning message "Hazard Warning Lights Malfunctioning". I then noticed that none of the other buttons on that row worked either (heated seats, air scarf). I replaced fuse 18 which blew again straight away. Mercedes must know about this issue which is a fire hazard.

 

[Stratman]

My enquiring mind would want to know why that component fried in such a spectacular manner.

Does it supply current to something? If so there could be a short in the circuit to it.
Has another on board component failed with the domino effect causing the fire?

I'd want to rule out an external short before putting three hundred quid in there, just in case. If you can, try to follow the PCB traces from the burnt bit, see if one goes to a connector. If if does, what does that connector feed? If you can isolate the pin, what does that pin feed?

 

[DrNick]

As as been said, replace the fuse with no board attached and (assuming it doesn't; blow immediately) check with a voltmeter the voltages on any pins on the connector, with ignition on and any switches needed to activate the suspect system on as well. Check that nothing is over the expected 12V. Its very unlikely (almost impossible) for this to happen, but then, this is an unusual case.
If everything checks out then I would switch everything off and carefully replace the board, and then switch back on keeping an eyeball (and nose) on the suspect area. Maybe even touch it to see if its getting hot. It might be that whatever the board is controlling has the problem, and this component is the one to give way first!