Headlights dim, blower fan slows when I tap on the brakes at idle -- bad alternator?

[Bright1]

Surely the brake lights don't suck down *that* many amps! Anybody got any idea why things might dim down noticeably just for a tap on the brakes? I'm hoping this isn't the symptom of a bad alternator... The idle speed doesn't slow at all, and the battery is only 4 months old. All suggestions / help much appreciated.

 

- Bright1

(Well, almost!)

[Cougar]

The brake lights do pull a fair amount of current but not as much as the other things you mention. With all the things going you mention, there will be a fair load to the system.

 

From the symtoms you describe it sounds like the battery may not be fully charged. I recommend you check the alternator output connection and the battery connections for a bad or dirty connection. If the battery connections haven't been cleaned with a battery brush you should do that. Make sure that the alternator output stud is tight and the connector is not burned. If you work on the alternator remember that the stud is always hot. Don't ground the connection unless the battery is disconnected.

[Tiny Clark]

If you have ABS, the brake system draws more current than just for the bulbs.

"The anti-lock brake system tests itself every time the vehicle is started and every time the brakes are applied. The system evaluates its own signals. If a defect is detected, the system then turns off, leaving normal braking unaffected."

 

My lights get dim at idle as well. Tap your RPM's up a bit to about 2 grand and see if you notice a difference. If so, you may have a problem.

[NOMAD327]

I've seen more problems of this sort come from bad ground connections or bad battery or battery connections than anything.