Help! i just got a '79 280SE.
 

i've just gotten a 280SE 1979 it has no owners manual.

just below the instrument panel to the left of the steering column are some lighted indicators.

One is obviously the battery/alternator red light indicator.

To its right is a yellow/amber indicator which flashes when i apply the brakes.

Can anyone help me understand what the indicator is and why it is lighting??

It is telling you that it is time to replace the brake pads.

Specifically, the front bake pads. Only the fronts have a sensor.

You need to order an owners manual from your local dealer. Call 1-800-FOR MERCEDES and register your car with them. Mercedes roadside assistance is free to all Mercedes owners no matter how old the car even if you're not the original owner. ;)