So, my blinkers stopped working all together so I replaced the bulbs and the fuse and voila... Fixed!
Uh, nope. only worked for a few weeks...
Now the left blinker only blinks once, maybe 2x and the R blinker works sometimes or only blinks a few times before stopping. If I hold the blinker arm "in between" the on/off position, I can sometimes get it to blink a tad longer.
It's dangerous not having properly functioning blinkers... I'd like to fix this right away. Is it the relay? The wiring? Do I need to replace the whole wiring unit? And if so, where is the best place to obtain these parts for an 88 240 DL? I have no idea where these parts are. The manual is very confusing.
Any help is very much appreciated.
thank you!

 

I think the fault could be in the blinker arm. Just screw open the arm and see if you can see some fault in the wiring.

 

anyone else have any ideas? Where is the location of the relay switch? Where can I buy a new one for this old beaut? Thanks!
p.s. Going to look at the arm, but wanting to figure out plan B and C if that's not it.

 

I could tell you where the blinker relay is on a 740 and 940, but I'd have to look up where it is on a 240.

Bentley says its to the right of the driver side foot well, just above the transmission hump, and behind the lower stereo/amplifier/equalizer mounting position.

this guy concurrs... http://www.davebarton.com/pdf/relay_87_240.pdf

 

thanks everyone! I'll let you know how this shakes out.

 

So, your problem may be unrelated to this, but, this side note may help--Many intermittent electrical problems I have found to be connected to the fusebox. I clean and sand the fuse and contacts for the tricky area, and magically things start working again. I don't know what it is about those style fuseboxes, but they are prone to oxidization. So even if I have previously replaced fuses, I often clean them up again before I move on to other things--it is easy to rule out and nice if it is the problem.

 

also, for the 240 'ceramic' style fuses, get the copper/brass ones... there's a vendor on ebay who sells a kit of way more than enough fuses, he targets this for Mercedes W124 chassis cars that used these (late 80s 300E family).