I would double check the wiring going out the polorator motor before anything else. Make sure there is continuity through the wires and double check your crimp connections at the motor end.
The pulse wire unless I'm totally out to lunch here is the wire that brings back the signal from the motor on the feedhorn to let the receiver know how many turns have been made and where the wire in the feed horn is pointed. I think it's just a magnet that spins past a coil. Never ever took one apart though, so could be totally wrong.
Let us know if adding the Ku was worth the effort. I'm just running my DVB receiver off
C-Band. Didn't seem to be enough English language programing on Ku to go to all the additional expense off buying a new dual band feed. Pansat has a Ku LNBF that is for a regular, non-offset dish that is not too expensive, but I'm not sure how good it would work duct taped to the old C-band feed horn.