make sure you check on both sides of the harness connection. i have seen just that connection be a source of unending frustration over the years, while guys replace turnsignal switches, and the problem remains because the terminals in the connection to the harness have issues.
before you pull the switch, unplug the connection and check just the switch wires. if that works out, chances are the switch is ok. [no real guarantee, but just maybe] then, look very close at the harness connection for issues such as corrosion, loose or woolied up terminals, or cracked wire insulation.