Skip the auto shop - Our mechanics make house calls

Q: Voltage drop noticed during night driving. The headlights dim and then return to normal.

asked by on

While driving at night notice headlight dim low and brighten up. Voltage shows drop for a second. Bad ground?

My car has 105000 miles.
My car has an automatic transmission.

A: This may be a sign of a failing voltage reg...

This may be a sign of a failing voltage regulator or potentially a bad ground connection. As you may know, the voltage regulator regulates the charging of the battery by the alternator. When the voltage regulator is not working properly, this will result in the alternator allowing too much power to be delivered to the battery, damaging the wires and prematurely destroying the battery.

In other cases, it may result in the alternator not supplying enough power to the battery, causing the battery to be undercharged or not charged at all. In either case, I would recommend having an expert, such as one from YourMechanic, come to your location to diagnose your vehicle's charging system and suggest the needed repairs.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Save up to 30%

Get a quote

What others are asking

Q: Antitheft system isn't recognizing key

The anti-theft system in your vehicle will prevent the computer from delivering fuel and spark to the engine if it does not recognize the chip inside your key. Your specific vehicle also requires a minimum of 2 keys programmed to...

Q: The remote or the inside unlock button will not lock or unlock doors

The door lock actuators that lock and unlock your doors can become weak and won't have quite enough power to fully move the lock mechanism inside your door. This can happen for a couple of reasons. The individual actuator is...

Q: Charning issues, new battery and alternator

Hello there. There are a few potential causes for why the car would have charging faults even after the alternator is replaced. The most common would be the battery cable, shorted harness, battery, or a failed alternator. The first thing...

Related articles

How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.