Q: Headlight on the passenger side keeps going out. Have replaced the bulb and the ballast.

Hi there. Check the harness to the headlight with the headlight switch on and see if there is a voltage present. If there is a voltage, then check for resistance on the ground side of the harness. If there is no ground, then there is a break in the wiring on the headlight circuit. Go to the ballast and check the wiring from the ballast to the light. If the wire has no resistance, then the break is in the wire between the ballast and the light base. If there is resistance, then check the wiring from the ballast to the main engine harness. If there is a break, then the wire from the ballast to the main engine harness needs to be repaired. If there is no resistance, then the main engine harness needs replaced. If you need further assistance with your headlights issue, then seek out a professional, such as one from Your Mechanic, to help you.