Battery losing power at idle

[headrush]

I've got a '97 4.0 SOHC and had this issue lately where I'll be sitting at a stoplight idling and my battery voltage will go up and down, up and down...my instrument cluster will dim and so will my headlights. I just replaced the battery and the alternator is about a year old. When it's doing this the radio is usually turned on, along with the ac/heat. Could my alternator be the culprit (I've still got it under warranty)?

Any help would be appreciated.

Thanks.

 

[my98nnj]

Could be a defective alty. Did you put a new surp. belt on when you changed the alty? How about the idler pully? They get week after some time and might not put enough tension on the belt.

 

[headrush]

Nope haven't changed either one...relatively easy fix/replacement?

 

[SoNic67]

Sounds like a bad alternator. The alternator is very easy to replace. Removing the belt might be a little tricky - auto stores sell alternator belt removal tools that makes the job easier.

 

[headrush]

Guess I'll get the alternator tested first and see what the results are. I take it the IAC valve wouldn't be the issue since it seems more related to the electrical part of my vehicle? I haven't cleaned it in a while but will tonight.

 

[SoNic67]

When my IAC valve was bad, wouldn't dim the lights. Just stall the engine if I wasn't pressing the gas pedal.

 

[headrush]

Ok I've had the battery, alternator and starter checked at two different auto parts stores...both say all three are working/running great. I've done a fuel injection cleaning and replaced the fuel filter recently...one guy mentioned the EGR valve being a possible source of the problem...any of you have any thoughts on cleaning/replacement?

 

[OneLever]

The battery cables themselves can corrode underneath the plastic insulation near the cable ends. I have read of this causing similar problems to what you describe on here. Worth a shot to look at.