Engine RPM drops when Headlights are turned on

[EG_Civic]

When I turn my headlights on, the idle drops probably 250 - 350 rpm. Is this normal? its not alot, I was just wondering if maybe the alternator is going bad. Any tips?


EDIT: I dont have a tach in the cluster, so Im guessing on the RPM, its probably closer to 100 RPM. Anyway, its enough to hear but it wont stall or anything.

[SilverY2KCivic]

Maybe have it checked out, but esp. on older cars, it's pretty normal as the headlights can and DO put a slight load on the car's electrical system, which inturn powers the car from the electricity that has to flow to the spark plugs to ignite the fuel.

[Tomsriv]

100 rpm is normal. If it drops a lot it could be due to a weak battery (it acts as a voltage buffer) or a worn alternator.

[EG_Civic]

Yeah, its closer to 100 rpm. If its normal, then I wont worry about it that much. Im gonna have to get a heavy duty battery/alternator anyway for my system.

[88_SC_CRX_Si]

There is a slight lag before the Electronic Load Detector (ELD) sensor can signal the ECU. To increase the fuel injector pulse width, to compensate for the added load. It can take ut to 3 seconds in some cases....

[88_SC_CRX_Si]

Might want to check the tension on the alt. belt, it could be slipping a tid-bit.

Just a thought...

[Ricochet]

It's normal as long as driving isn't effected..

[SRV BOY]

Thats normal, my rpm drops when I use the power windows and sunroof, and I just put in an
ac delco heavy duty battery.