Skip the auto shop - Our mechanics make house calls

Q: When my car starts I see my headlights and indash lights go dim.

asked by on

I also notice that when I turn my key to "on" my sub in my car makes a bump every few seconds even without using my stereo.

My car has 88000 miles.
My car has an automatic transmission.

A starter motor uses a lot of current and thus will cause a voltage drop at the battery. During the brief interval that a starter engages and runs, any other circuits that are also "on" could see the voltage drop and, in the case of lighting circuits, bulbs will dim. The dimming will be more pronounced if the car battery is old and/or the car wiring has poor ground connections, and high resistances, much of which come with age. You should have the battery tested in a load test. Batteries are very important. If the battery only has a marginal pass on the load test you should just simply install a new battery to reduce diagnostic headaches. Charging system output should also be verified against factory specifications To have the alternator inspected please request an alternator inspection/replacement and the responding certified mechanic from YourMechanic will get this resolved for you. As far as the sub, the problem you are describing may mean the system is powered when it is not supposed to be. That would have to be investigated in an electrical diagnostic. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

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

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: How do I get radio information for the station/song that's playing

Hi, More than likely, your stock stereo does not have the capability to display this information. It's only been within the last few years that nearly all new vehicles display the song/artist playing on FM radio. If you want this...

Q: Charging and starting - 2008 Chrysler Sebring

Code P0622 relates to the alternator not working properly. This code can sometimes come up when the battery is weak. I would recommend testing the battery first and if it checks out OK, then the problem is likely the alternator....

Q: Belt tensioner

If the tensioner lock bolt broke, then drill and use a reverse extractor to remove the bolt. The tensioner bolt should then be replaced with the new tensioner and belt. If you'd like assistance on this repair, a certified YourMechanic...

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...
P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...
What are the Car Pool Rules in Hawaii?
Hawaii is widely regarded as a land of vacation and relaxation, and as such, its scenic roads and routes are far better known than the state’s freeways. But, as with all...