what year 240d? Sounds like your hazard flasher switch in the console.....but depending on the year, you may have a seperate relay...just forward of the shifter, I think?

I just replaced mine (1981) - everything is built into one unit (thus the $90 cost) and it controls everything. Lots of info on here about cleaning them out too, many times they are dirty with years of abuse.

I'd check your fuses/bulbs first (vac. has nothing to do with your problem).....pull the hazard switch next....and if that doesn't work, check your grounds.

This is common problem - tons of info here on the forum to guide you.

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1981 240d - 135k - Arlene