Symptoms: Battery goes dead after running, not when sitting and turned off. Battery will set for days and days but still hold a strong charge. Run it and it will not last three days before dying. I think I've ruled out a parasitic drain. I hope. Battery was replaced brand new. Still acting up.

Alternator was replaced brand new after I thought this was the problem. Still acting up.

Serpentine belt replaced after I thought this was acting up. Still acting up.

The ground to the body from the neg terminal was cleaned and reapplied. Still acting up.

I am frustrated to say the least and need help figuring this one out. The lights pulsate at idle. Increase the RPM to 2000 and they quit. Seems like the alternator is not charging the battery. Garage said everything metered real good. I don't know what to look for next to get this fixed. I appreciate all the help.

Jamie

 

Battery holds a charge for days. So no drain when sitting.
Run and battery dies.
Logically, it says that the alternator isn't charging battery.

Replacement parts don't always mean good parts.
But, I think there is another problem here

This would have shown up in other ways.
But, still good to replace old belt.

Okay, think you are on the right track.
Did you clean the terminals on the alternator cables? Especially the ones going to the battery?
Did you clean the battery posts?
Corrosion isn't always visible.

Yeah, alternator is not charging the battery.
New alternator may not be working right.
Could it be the sensing line?
Still would go with cleaning cables and terminals on alternator and battery.
Then see what else is going on.
If problem still exist then would looking into alternator

 

The garage said the alternator was metering good at @14.5 or so. No discernible fluctuation. They also said the alternator was sensing the battery and the flow was within spec.

I was wondering if the sensor in the neg terminal cable may have went bad but not completely gone. I cannot find where this could happen. They either work or do not is all I can read anywhere.

I've scrubbed the terminals too much it seems. But I will try it one more time.

The pulsating lights are rhythmic and not erratic too. If I bring the RPM's up to 1500 to 2000 the pulsating goes away. I cannot find a link between the alternator and the battery that could point to a possible location of failure.

 

Alright, so, Maybe there is a link between the tensioner pulley and the fluctuation.

So, when the car is at a warm idle, the tensioner pulley throbs in rhythm with the lights. When I increase to 1500 RPM's, the throbbing of the pulley and the pulses of the lights go away.

I'm wondering if the pulley is bad or if the increase in RPM's just makes both of them smooth out.

Any takers???

I've checked wires over and over again. I can't find the draw anywhere. If I turn on all of the accessories, it's still identical. No increase in draw down or anything pointing to a fault somewhere.

Could it be the tensioner and is this a common thing that goes bad? I've never heard of a tensioner going bad.

 

I think you have found your problem

 

It is a recommended procedure to replace the tensioner when the belt is replaced.