alternator??

[jrSS]

Why do my headlights dim and my blower for heat or a.c. bog down when stopped?? Could it be the start of a bad altenator?

 

[Joe D 04]

Yes... it could be. Most of the time its the alternator. Does your battery gauge move at all when it bogs? do the headlights sometimes flicker while driving or decelerating?

 

[The_Roadie]

Or loose/corroded/oxidized cable connections at the alternator, battery, fuse block, or grounds in the engine compartment. Do you have a hand-held voltmeter? Have you inspected the cabling?

 

[jrSS]

Nope haven't checked anything out yet....BUT now that I know what to look for I'll check it out.thanks!!

 

[RayVoy]

It could be any one of the electrical connections talked about above.

The alternator keeps the battery charged; but not to just have battery power to start the truck, the battery is a power reservoir.

The energy, in the reservoir, is called for whenever the alternator can not keep up with the electrical demands.

The output form the alternator is high when the engine rpms are up, when the engine ides, the alternator output falls off; and, if the current demands are high )blowers, lights, speakers) the battery must provide the current the alternator can not provide.

So, you might have a weak battery.

One other possibility, the idle rpms maybe falling below the "normal" idle rpms. If the idle is falling below the normal, of about 625 rpm, the throttle body may need cleaning.

 

[Arock]

FYI It could also be the electric fan clutch is on its way out. The same symptoms that you described were what mine did for about a month before until it finally failed and locked up. It about drove me crazy trying to determine where the electrical drag was because it didn’t stay consistent, no check engine light and it didn’t sound like the fan was locked up.