Great info in this forum. Hope I can add positively to the contribution of ideas.
code reader
So I needed a OBD I blinker code reader for my 94 until I get the actual scanner. Wanted to check to see if there were any codes although my check engine light is not on. Found this thread on how to make a code reader as well as several others and proceeded to make my own.
I wanted to share my findings in the event that others may find them useful. I kept things Mercedes, rather than get the requisite parts from radio Shack, and to keep an MB flair I opted to re-purpose a common Mercedes dash switch for this tool. In my case I had a spare w124 Rear Window Defogger switch, but a Air Recirc switch or likely any other MB momentary dash switch with LED indicator would work.
Open the switch and make a few changes with a soldering iron. All the parts you need are already in the switch. The RW Defogger switch has (2) LEDs, and (2) LED resistors. Add a small wire connecting bridge and your are done. Same holds true for an Air Recirculation switch.
Tester works like a charm, tested and came up with 1 blink across all areas, No Codes
I attached a couple of pics for your reference. The Probe lead (for 8 & 14) is the one side of the switch contact and ground is the other. Enjoy
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EDIT
If you really want to get snazy and either have an extra spot on your center console switch assembly or simply dont need a RW Defroster. you could wire the switch directly to lead 8 and 14, and since this switch is a double trow momentary, you can read your fault blinks from the comfort of the cabin, one direction for pin 8 and the other for pin 14.