My voltage drops only in gear when stopped at light with the headlights on.

Hi, my name is Devin. I am an auto repair expert with the Car Genius team here at RepairPal. I'm sorry to hear you're having trouble with your Ford Focus. It sounds like your alternator might struggle to keep up with the electrical demand, especially when the vehicle is idling in gear with the headlights on. When the engine is idling at a low RPM, the alternator doesn't generate as much power, and with the headlights and other electrical systems drawing current, the voltage can drop. If your alternator starts to go bad, it might not be charging the battery effectively at low RPMs, leading to voltage drops. You could also check the condition of the drive belt, as a loose or worn-out belt can reduce the alternator's ability to charge the battery correctly. If the alternator is indeed failing, it would need to be replaced or repaired to resolve the issue. If you need more advice, have any other questions about your vehicle, or would like to get connected to a RepairPal Certified shop near you, we have you covered. Give us a call at 877-913-1554, and we will happily help you out!