Dear friend
First have a multimeter handy, leave the flasher unit connected, but separate a bit it’s Bakelite connector from the harness to check each of the leads.
Below attached on this post you will find a picture of the back of the standard Bosch flasher used on most mercedes of the era. Double check that you have the same unit, as position of the pins may be different if not this particular model.
There are 6 pins.
This is what you should be looking for:
1. Terminal labeled 15, should have power only with ignition on
2. Terminal labeled 30, should have power all the time
3. Terminal labeled 31, should have continuity with chassis ground
Then you have the output terminals,
First, there are two terminals labeled “L” and “R” which are the output signals for the left and right turn lights when you activate the hazard relay for an emergency. Pull up the knob of the flasher relay with ignition off and see if you have a pulsed 12v signal on each of these leads.. for that put your multimeter in DC voltage on a range close to 12V (50volts for example) which is what you are looking to measure. Put multimeter negative lead on a good ground and the positive lead use it to touch the flasher terminals L & R.
Now if above test was successful go for testing the flasher turn signal function. That function needs the terminal 15 to be energized, and the steering wheel switch should be activated pointed towards the LEFT or RIGHT. Ignition ON in order to have power on terminal 15.
Put your multimeter positive lead on the terminal labeled “49a” of the flasher, keep your multimeter negative lead on a good ground and see if you have a pulsating 12v signal.
Enjoy your experiment.
Best regards
L.peterssen
