Q: Turn signals don't work right when I have headlights on but when there off everything works right

If the turn signals and headlights are both activated by the same column-mounted "combination switch" a possibility is there an internal fault with that switch. If the two circuits are not working off the same "combination switch", there is some sort of electrical issue possibly involving a voltage drop (when the headlights are on) that is large enough to make the flasher unit malfunction. All these possibilities can be quickly checked with reference to the factory wiring diagram. To get all the lights functioning normally, reliably and safely, if you want the required diagnostic and repair steps performed by a certified Mechanic, dispatched by YourMechanic right to your location, please request an electrical component/circuit diagnostic. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.