Probably the brake switch or associated wires. This switch is typically located near the bottom of the brake pedal, probably under the floor of the golf cart. The rear tail lights are LED which is why they are sealed no replaceable parts. I have the equipment to test the switch, I also have a 2017 Yamaha, and i can take a look and see where the switch is located. I am in Pinellas, and could look at it over the next couple of days. Send me a PM if interested.
__________________
Pennsylvania, for 60+ years, most recently, Allentown, now TV. 
|