HELPPPP ME

ok, i have an 87 GT and heres my problem... my signals dont work, ive checked the following...fuse, flasher (changed both of them), connections to switch all seems fine (also the owner befroe me installed a new multimalfunction switch not too long ago)
i recently chenged my headlight switch and put in a repair harness, after instalation i checked and the signals worked, i went out to the car the other day and discovered the problem
the hazards also work (the dash and exterior lights work), as does everything else on the same fuse (backup lights, defroster etc) works
HELP ME IM STUMPED what else am i missing and could i check
PLEASE and suggestions at all