Weak electrical...

[Whoru465]

I recently noticed that when I turn on my headlights, the engine revs drop ever so slightly. Dosn't really show much difference on the tach, but I can hear it... Any thoughts? Thanks





-Mike

[dcarrb]

Not unusual. It's caused by the load placed on the alternator when you turn on the lights. Shouldn't be a problem as long as it's barely noticable, but could indicate a weakening battery if it becomes pronounced, or if the lights brighten considerably when you rev the engine.


dcb

[Chiketkd]

Honestly, I'm thinking it could be an early sign that your alternator is on the way out. If it is, your battery will be drained when your car is running and eventually it'll go dead. Take it to a place like Autozone or Advanced Auto Parts and they'll check it out for free.

If it is your alternator, you can buy a re-manufactured one on Ebay for pretty cheap (~$40-$50)

-Chike

[Mr. Pockets]

Originally posted by Chiketkd
Honestly, I'm thinking it could be an early sign that your alternator is on the way out. If it is, your battery will be drained when your car is running and eventually it'll go dead. Take it to a place like Autozone or Advanced Auto Parts and they'll check it out for free.

Those tests aren't exactly foolproof. I mean, the machines say right on them not to run them for more than 3-5 seconds. That's simply not enough to pick up an intermittent problem.

As a matter of fact, I think these alternator and battery testing stations the parts stores use only hurt their business. My friend was having a problem with his car. He took the alternator in and had it checked. They said it was good. He had his battery checked and they gave it a clean bill of health, too.

We replaced his alternator (and battery, eventually) anyway and the car ran perfectly after that.

[Chiketkd]

Very true. Those tests definitely aren't fool proof.

-Chike

[oab_au]

Originally posted by Whoru465
I recently noticed that when I turn on my headlights, the engine revs drop ever so slightly. Dosn't really show much difference on the tach, but I can hear it... Any thoughts? Thanks

-Mike

Hi Mike, like Dcarrb says, thats normal.

The lights pull about 11amps, the battery voltage drops, the voltage reg senses this and turns up the charge rate to balance. The engine doesn't put out much power at idle, so the rpms drop and the IAC picks it back up again.

Harvey.

[Whoru465]

Thanks fellas. Its good to know that some of this stuff is just the car's...oh....quirkiness... I'm going to keep an eye on the battery charge, etc. Just in case. I'm sure it will be fine.





-Mike