Couple things going on...lights dim..belt noise

[SRT-440]

First, at night when at idle the headlights/tail lights seem to dim..and bring the RPM's up and the lights get brighter. I know sometimes this is normal..but this seems a bit much.

Second, when I rev it up some times I can hear what sounds like a belt squealing.

Battery is crap and needs replacing..holds a charge but will go dead after a few days of not starting.

Are these indications of a bad alt? Can a bad alt effect actual spark in the distributer?

Whats a good replacement?

Thanks! 

[2Gunz]

Its possible that you do have a bad alternator.

However I suspect its just the battery.

Stock alternators dont charge well at idle.

Your lights being extra dim is a result of the battery being dead and the car having no reserve power.
The alternator would like to make up for this, but cant very well at idle. So the voltage difference between
idle and say 2000 Rpms's is more noticeable than normal.

The more the alternator need to charge, the more torque is required to turn it.
So when you have a good battery the belt tightness is fine.  However with a dead battery the belt is
not tight enough and slipping.  Hence your belt squeal.

The alternator can have an effect on the amount of spark at the distributor.
This comes mostly in the form of low voltage. The lower the voltage the less spark.
In a normal situation your looking at about 14 volts for the cars electrical system.
With a dead battery the alternator does what it can, but the voltage will be low until it can charge the battery.

There are many replacement options. From stock to aftermarket and a combination of both.
A search on this website should provide a lot of information.

Go get a new battery and I suspect your troubles will go away.


ME

[Chryco Psycho]

I agree the belt squeal is the alt trying to charge the dying battery , with the battery weak the alt is working harder to keep up . Change the battery !!

[SRT-440]

Thanks guys, gonna get a red top for it this weekend.

[68neverlate]

First, at night when at idle the headlights/tail lights seem to dim..and bring the RPM's up and the lights get brighter. I know sometimes this is normal..but this seems a bit much.

Second, when I rev it up some times I can hear what sounds like a belt squealing.

Battery is crap and needs replacing..holds a charge but will go dead after a few days of not starting.

Are these indications of a bad alt? Can a bad alt effect actual spark in the distributer?

Whats a good replacement?

Thanks!  

Interesting that the battery goes dead after a few days of not starting the car... could suggest you have a draw somewhere.  Can also be a bad alt as Gunz and Chryco indicated too.  The dim lights at idle is common with a stock alternator... it's a design issue that leads to low output at idle, even with properly operating components.  But if it's more than usual, it could be that your alternator output is low/nonexistent... take a voltage reading at the output stud of the alt with the engine running... you should get between 14 and 14.5 volts if it's good.  

If you want to know if you have a draw and you have an ammeter, disconnect the negative battery cable from the battery post (engine off) and place the ammeter between the two.  The draw should be minimal.  If not, then there's a draw issue to track down...

The draw could be the alternator... it's possible that it has developed a short and is causing both issues... low/no charge while the car is running and a draw on the battery when it's not running.  To check the alternator for a short, disconnect the wire(s) from the output stud and perform a continuity test between the stud and ground (engine off of course).  If it tests positive, the alternator is bad (and your battery may not be)...     

Just thinking out loud...        

[68neverlate]

Hmmm... read your symptoms again and had another thought.   

You sound like you're getting the lights to go brighter on rpm increase so alt sounds like it's charging, at least to some degree.  So, dimmer lights than usual at idle, squealing belt on rpm increase.... could be a bearing going down in the alternator.     

Course, if that's what's going on, then there's another issue causing your battery to go down...   

[SRT-440]

This weekend I'm gonna address this...but the battery in it is beyond tired...I'm leaning towards the bearing in the alt and a really weak battery. Gonna test the alt and replace the battery and will update the thread...but all the suggestions are possible...process of elimination I suppose.

[myk]

Gotta go with that 90amp or higher 'alt setup!

[SRT-440]

Anybody know a good place and part # for a better than OEM alt?

[68neverlate]

If you're going with a higher output alternator, be sure to upgrade your wiring (heavier gauge) to handle the extra output... lest you risk burning up your existing wiring/ammeter.  You need to be careful about your ammeter even if you do upgrade the wiring... I'd recommend a bypass (wiring modification) to protect it.  

There's lots of threads dealing with both of these things on the site... search on "alternator output" on this (Electric, Gauges & Lights) board.        

[myk]

Here's one, I think...http://www.dodgecharger.com/forum/index.php/topic,168.0.html

[mhinders]

Start with replacing the battery. A lead-acid battery that has been left in an un-charged state is quickly going bad, and goes sometimes into internal short circuit. Typical behavior is that it doesn't take charge, not more than a fraction of its original capacity. A voltmeter would still show high, full voltage, but there is very little energy in the battery.
Usually there is no need for a bigger capacity alternator, unless you have added lots of power-hungry electrical stuff.