Inconsistent interior lighting, alternator dying sign?

[alkemist]

Sometimes, actually rarely I notice my interior lights, including dash, changing brightness. Looks like brightness corresponds with minor motor RPM variations. SO anyway., the battery is new..... if the lights are not contant enough, is this a symptom of a dying alternator? Otherwise, theres no bearing noise everythins ok


thank you

[UncleBob]

depends on the amount of load you have on the electrical system at the time, the output of the alternator, RPM of the engine....etc....etc. Some systems, with enough loads, will have lowish voltage at idle.

You need to have the alternator tested if you really want to know for sure. Many autopart stores will do it for free. Takes seconds.

[curtis73]

It could be a voltage regulator that is out of spec, or possibly a just low output from the alternator. Its not cause for replacement, but I might test the output of the alternator at idle and at 1500 RPMs. As long as its above 14v at 1500 you're fine. If its dips below about 13.5 at idle its fine as long as you don't idle enough that your battery suffers. If it drops below 13 at idle I might start keeping a close eye on things.

Basically, as long as you don't have any issues with starting, charging, and the everyday operation of the car, then its normal. Up until the 70s, cars did that all the time, but voltage regulator technology, alternator outputs at low speeds, and voltage stability have improved greatly which is why you're not used to it.

[alkemist]

Originally Posted by curtis73

It could be a voltage regulator that is out of spec, or possibly a just low output from the alternator. Its not cause for replacement, but I might test the output of the alternator at idle and at 1500 RPMs. As long as its above 14v at 1500 you're fine. If its dips below about 13.5 at idle its fine as long as you don't idle enough that your battery suffers. If it drops below 13 at idle I might start keeping a close eye on things.

Basically, as long as you don't have any issues with starting, charging, and the everyday operation of the car, then its normal. Up until the 70s, cars did that all the time, but voltage regulator technology, alternator outputs at low speeds, and voltage stability have improved greatly which is why you're not used to it.

beautifully said thanx