Turn signal lamps do not work - how to repair?
 

Check the hazard switch.

Which car are we referring to? The 123 or 126?

The 123 cluster pins are
14 - left
13 - right
15 - ground

I don't have a diagram handy for the 126 2nd gen but it might be similar to a 124. The 124 cluster pin assignments are
14- left
15- right
1- ground

Numbers should be imprinted in the plastic of the connector head. Might need a magnifying glass.

Or just hit the 4-way flasher switch.

If you are doing any testing with the key in position 2, unplug the glow plug relay first.

I usually take the cover and lay it on the console so I remember to plug it back in when I am done.

One more thing, that D-shaped key is very easy to break off.

If it does get broken off, you can still plug it in but you have to be very careful not to get it clocked wrong.

This happened on my 124, so I have a white paint mark on the connector and the circuit board to line it up. The numbers are on the PC board too so you can figure out where it should line up.

Check the bulbs, move them back and forth till they light...with the lever position to the correct side or hazard switch pressed...

one common fault which might cause this problem is a broken ground connection inside the cluster. the solution in that case is to add a supplementary ground wire. i think it has to touch all three sides separately, then go to the chassis.

A test light will do fine and is sometimes easier to get to the connector than a multimeter (that long, thin probe can be helpful), though the meter's OK, too.

Remember that the turn signal needs the resistance of the bulbs to work. Turning on the 4-ways sort of bypasses that need and will let you troubleshoot the dash bulbs easier.

In general, all weird electrical issues eventually lead to ground issues. Once you've eliminated dead bulbs, dirty sockets, broken wires, etc. go looking for grounds.

I'm giving generic advice learned from many years of working with American and Japanese cars and may or may not apply to M-B - Bosch electrics are a mystery to me.

Dan

The vast majority of all complete turn signal failures are the emergency flasher switch. For some reason the circuit to the turn signals flows through the emergency flasher switch. The console switches tend to collect dirt and liquid spills causing the internals to fail to make contact. Many times you can switch the EFS back and forth several times and it will clean the contacts enough to get the turn signals working again. Before doing anything else concerning your turn signal problem, most of the board would advise you to remove the EFS, disassemble, clean all the contacts, then re-install.