RE: 2001 SLK 230, R170

My Fog Lights stay ON when the switch is turned to OFF and the key is removed.

Is there a relay in the fog light circuit?

Before I buy a new switch, I want to confirm that the fog light relay is not the culprit.

This happened while on an overnight trip, so in order to save the battery charge, I removed the fuse, which only controlled the fog lights, thankfully!

My “logic” says that the only way I can see that power is always ON in the circuit thru the fuse to the fog lights is if there is a short from power to the fog light’s switch leg. Hopefully, someone who is much more technically savvy that I am can answer this question for me!

Please advise and Thank You!
Bob

You can also try slkworld.com

I don't have direct knowledge of these cars, but based on 1997 era cars, the fog light switch only sends a signal to the body computer then a relay or transistor is triggered turning on the light.

If relay, it might have stuck and could be cleaned, if transistor replacing the body module is a more direct route unless you have electronic and soldering background to diagnose and repair.

In any event, be sure to post the results here to help others in the future.

My car always does this, for about a minute. Yours stays on forever?

__________________
1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra