I have a 2007 mustang coupe the wind shield wipers wont turn off

Could be a fault with the self park switch that is integrated into the motor or perhaps the wash/wipe sweep timer relay. It depends on how it is wired but unplugging the relay might stop them or it might not and even if it does it isn't likely to prove anything. Substituting a known good relay is the best way of testing and if that makes no difference I suggest checking the motor self-park switch next.