Dimming lights question...

Question

I have a 2004 Civic that I bought used, so repair history is unknown.

If I close the power windows or sunroof, the headlights dim. If the a/c cycles, they dim etc...

Is it alternator or battery or not sure? LOL

Thanks!!

Answer 1

a/c cycles and they dim ? My educated guess is the alternator or regulator!

Most Mechanics can do a charge test and see if the regulator and alternator are playing well with each other !

When engine speed affects the lights, that's the charging system.

Battery, alternator, regulator if your car has one.

EDIT: I see you got some good answers already !  

: )

At least your car doesn't have some strange Bugs in it !

Answer 2

It's either the alternator or the serpentine belt is loose, which can also make your alternator go bad.

Answer 3

The alternator is not supplying enough charge. This could be the regulator, worn commutator/brushes, bad wiring, slipping belt (usually accompanied by loud screeching), or the battery could be shorting internally.

Seeing as the car still starts and runs, the battery doesn't seem to be at fault. If there is no screeching or burning rubber smell from under the bonnet, I'll assume the belt is fine.

Seeing as it's a 2004 Civic, I'll assume the alternators commutator and brushes are still good(it's rare for them to wear out), so you're looking at a faulty regulator or damaged wiring.

A regulator should be pretty cheap, and usually only takes two phillips head screws on the back of the alternator to replace, so unless you're a whiz with a multimeter to check for bad wiring, I'd suggest trying that first.

Answer 4

maybe clean the battery terminals or have the battery tested