72 c10 wire attached to cluster light

[tim21391]

Hello all... Started cutting rust and redoing my truck back in 2008.. Lost my license in 09 thru 11 truck sat maybe a year or two and has sat for awhile til I feel the need to drive... Currently I've been driving it and noticed the gauge lights weren't working at night... Long story short I bought another cluster and took both and made one... Every gauge finally works now and so does the gauge cluster lights... Prior to me doing this tho I had a bulb socket on the back of the cluster that had a black wire attached.. That I traced it and went up into the column.. Found that the wire was broken and tore my column apart to see where the other end was and I was shocked I couldn't find anything so I stuck a regular bulb and socket in the place and everything seems to work fine... Anyone have an idea where that wire leads to?

Thanks
Tim