My kids mustang decided it wants to have one light on all the time. It's the right signal/parking light. It happened today. He tried disconnecting the battery, and it was on when he reconnected it. Plugged and unplugged it, switch on and off. It stays on and solid light even when right blinker Is turned on. We just took the light bulb out for now. Base model v6 if that matters, 190k miles roughly.