Mercedes w124 Bulb Circuit Not Working

[krm712]

I as you can see in the image attached, I have this part removed as I tried to diagnose what happened. I had 2 old bulbs which I ordered and tried to replace as they were old and dim.. when I removed the bulb I found that the blue wire was in the left bulb holder when the old bulb was attached. When I tried to fit the new bulbs they worked how ever one was working and the other wasn't. I figured putting the wire back as it was (Strange as I have no clue what the wire is for) how it was. The bulbs aren't turning on anymore. They still work as when I connect them to the blower adjustable knob and the vent knobs they work perfectly fine.. So I'm assuming something is wrong with the circuit. What is the wire for and how can I fix my issue?

Thanks.

 

[mattkh]

Please put up a picture of the back of the old bulbs that you removed.

 

[mioba]

Looks a rather odd wire and perhaps added by a PO. Looks out of place as does the solder joint.