Why Car Lights Flicker And How To Fix It


Vehicle electronics are difficult to diagnose and repair, especially if several elements or connecting wires fail at once. However, a modern car without electronics cannot exist and the driver is obliged to keep it in good condition. If there is such a problem as flickering headlights, it is necessary to identify its cause as soon as possible and eliminate it, which will be discussed in this article.

How The Car Lights Work

To solve the problem with flickering lights, you first need to understand how they work. Like all electronics on a car, lights operate at a constant voltage of 12 Volts. 

The voltage is transmitted by means of a solid wire that carries a positive charge and a negative charge which passes the body of the car.

Why Car Lights Flicker

Flickering can occur to the headlights as well as any other lamps in the car. 

The main reason for flickering headlights when idle or driving is voltage sag, the voltage can sag for several reasons:

1. Defective Alternator

This is the most common reason for flickering lights, when one of the three rotating plates that generate electricity wears out, it starts hitting “dead spots,” and the power wanes, causing the lights to flicker. 

How To Fix:

  1. Make sure to check the alternator voltage, which may vary depending on the vehicle type but is usually around 14 and 15 volts. 
  1. If the alternator is faulty you should check the voltage regulator first (Most alternators since the 1970s have internal voltage regulators.). It is inexpensive and easy to change. If replacing it does not help, replace the diode bridge. And if that doesn’t help, you have no other choice then to replace the whole alternator.

2. Faulty Battery:

The battery may no longer hold the voltage. In that case, it must be serviced or replaced. 

How To Fix:

  1. Test the acid level of the battery and check the charging capacity. A battery that lost its ability to charge correctly can cause a weak flicker in the lighting system. In some models, a single positive lead wire goes into the nearby junction box.  The box can corrode because it is always beneath the battery where the acid is collected. When corroded, the junction box does not allow for a full current transfer, and when the car is in motion, the junction box may wobble or bump.

3. Worn Out Ground Strap

When your ground strap is damaged or wearing out, the electrical circuit will encounter resistance when trying to deliver power to the headlights of your car. As a result, you will likely notice that your headlights are either flickering and/or dimming on a regular basis.

Many electrical elements on the car depend greatly on ground connections, including the ignition system. Wobbling bolts or intermittent connections may trigger flickering of the lights.

How To Fix:

  1. Your ground strap (as well as the main ground wire of the battery) may be a little loose and will require you to tighten it securely. Otherwise, you’ll need to replace it completely if it’s damaged or worn. 

4. Xenon Lamps

If you have a xenon lamp and it started flickering, its a sign that it will stop burning soon. It may also indicate a problem with the ignition unit. 

How To Fix:

  1. To understand exactly what the problem is, you need to change the lamps.

5. Overstressed Wiring

This is rarely the case with modern cars but can still happen. For example, powerful audio equipment and heating can cause the headlights to flicker due to voltage sagging.

If Nothing Worked

If flicking lights still persist even after checking all of the things above, it can be assumed that there is a problem in the general wiring of your car. In such a situation it is necessary to contact a specialist, but keep in mind that the search for faulty elements in the wiring is a long process, which will take a lot of time and, consequently, you will have to pay a lot of money for the work.


One way or another, you shouldn’t put off fixing light flicker. Such a problem indicates that all electrical systems do not work properly, which will cause the bulbs to wear out faster, causing increased stress on the battery and other components. If you do not want to spend large sums of money on repairs in the future, take care of repairing the defect in advance.

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