If the lights turn on when you move the signal lever, it's obviously working. When you have a problem on just one side, suspect a bad ground wire, some other wiring problem, or a burned out bulb. Typically, with the newer and expensive electronic flasher assemblies, that results in it flashing twice as fast as normal as the indication of the open circuit.
When both sides act the same way, the best suspect is that electronic flasher. This is not always true, but if you see that all the outer turn signal bulbs light up, that is proof the bulbs and wiring are okay.
Normally I'm not in favor of throwing random parts at a problem until testing shows it is needed, but in this case that is the fastest way to diagnose the cause of the problem. If it proves to not be the cause, the cost is relatively low compared to an hour of a mechanic's time, and you can save the flasher for when it's needed in the future.
If a new flasher doesn't solve this, tell me if the outer lights and the dash lights turn on or do not turn on when you flip the signal lever, and I'll look up a wiring diagram to figure out where to go next. State whether the hazard lights and brake lights work too.
Monday, January 4th, 2016 AT 4:01 PM