need help with charging system problem

[yob_yeknom]

Something is wrong with my charging system. It started off small, but the problem is becoming more and more apparent as time passes. Here's the deal:

With the engine at idle speed (whether sitting there idling or just cruising down the road not giving it any gas), when I turn on the blower fan for the heater the ammeter needle drops with the different settings. It drops A LOT when I turn it on full blast. It also dims the headlights and all of the interior lights, the higher the fan setting the dimmer the lights. Pushing the brake pedal and having the brake lights come on triples the effect. After about 10 seconds of the same engine speed it goes away, but as soon as the RPMs change it will start again.
When going down the road, I can actually see the lights get dimmer and brighter with engine speed if the blower is on the two highest settings. It stops when I get above 2,000 RPMs, having no affect on the lights.
When slowing to a stop (brake lights on), even with the blower off, the engine will almost stall as the RPMs drop below 1,200. The lights dim very noticeably and the ammeter drops way down. The engine will struggle to keep itself running at around 500 RPMs. After sitting at the stop for a few seconds, RPMs will pick back up and the lights will get bright again. Having the blower on makes it even worse and takes longer to recover.
The battery doesn't seem to need charging since it has no trouble cranking the engine.

I don't have the time or money to just start replacing different parts of the charging system, so I'd like to get it right on the first try. I'm hoping someone will know the exact problem given the information provided. So where should I start?

Thanks.

 

[MSTNGGUY88]

Sounds like maybe the voltage regulator is bad. I know om my explorer it's built in the altenator. Take a volt meter and hook to the battery while the motor is running. It should read around 14 volts if the altenator is charging right. Have someone rev the motor up slowly to around 2000-2500 and see if it goes up or drops. Hope this helps. If this is the prob them it isn't expensive to have fixed.

 

[Bill Kemp]

If you have an Auto Zone or such parts store they will check the batery and alt. for free. The alt they can check on the veh. You may have to take the battery out. At least you can pinpoint the trouble and decide what to do next. Cost...$000

 

[Alec]

It's probably the alternator, or maybe more specifically the volt regulator, as was mentioned. It sounds like there's just not enough juice at low RPMs. You'd know if it was the battery (hard starts, etc), so I'd say the alt.

I also second the Autozone Idea. They're very cool about free checks, and their alternators are well priced.

 

[Jefe]

Sears will check out your 'entire' electrical system with a computer system. Not sure if it costs anything, but when I went in with a dead battery on my old truck they ran it to make sure it was actually the battery that was dead.