A faulty headlight can be a dangerous problem on the road, and it is one that you should address as soon as possible. Flickering headlights may be caused by a number of different issues, including a faulty light switch, the alarm module, or even the car’s battery. Some drivers find these headlights flashing when car is off annoying, while others see it as a sign that their vehicle is starting to break down.
A common cause of headlights flashing when the car is off is a drained or dead battery. Performing a simple battery test by checking the voltage of the terminals can help to determine whether this is the case. A good battery should read between 13 and 15 volts, while one that is low will typically only read 9 volts or lower.
If the battery is not the issue, a problem with the headlight switch or wiring harness may be to blame. It is possible that the headlight switch has started to malfunction, or the wires have become corroded and worn over time. This can cause the switch to open, close, reopen, and reclose in an effort to provide power to the headlights. This can also lead to a short between a ground and the headlight circuit, and this is usually the source of the headlights’ flickering.
Another way to diagnose a headlight problem is by using the scan tool to turn the lights on and off. If they remain off despite this, the problem is likely with the specific controller input for that headlight and should be addressed by a qualified technician.