I recently acquired a 1989 300E in good condition. It has a few things I haven't figured out yet, but what the heck is that little red light on the dashboard cover where it meets the lower left corner of the windshield? Could it be part of a forgotten security system? For months the red light shone steadily. Today I disconnected the battery to do some work. When I reconnected the battery the light flashes continuously. Three flashes, pause, three more, repeat. Anyone know what's going on?

 

I think that's an aftermarket alarm? I've never seen the light in the situation you see it in on a 300e before.

 

Well, I solved my own problem, sorta. I found a hidden toggle switch under the dash. By flicking it when the engine was running the blinking red light shut off. I assume I disabled some sort of aftermarket alarm system. As far as I'm concerned it can stay off forever.