(Just a thought)
Briefly looking at
http://ww2.justanswer.com/uploads/RoadsideJerry/2010-05-26_223414_speedo_1.png:
At the top left side of section [D], the 'dir flasher' feeds a common (+) dark blue wire to both the turn and backup switch circuits.
The open might be inside the flasher, the blue wire, or the connector where the two circuits split off.