Weird Charging Issue (1 Viewer)

[470SNC]

So my 99 LC has been running great for the 4 months I've had it. I was sitting in traffic on my way to work, see that my battery light is on and check the ultraguage and it reads 11.8 volts. I immediately rev it up to see if it still charges up (it does) and when the traffic cleared up, it charged all the way back up to 14 volts. The battery holds the charge when I turn off the truck and left it for 2 days. Started up like a champ with 14 volts.

Now I had the battery, starter, and alternator tested and everything is good. Truck runs and charges normal when in normal traffic but as soon as I'm in stop and go brutal freeway morning traffic, it drops rapidly and the charge cant keep up. Any ideas on what the issue could be? Maybe the volt regulator? Alternator? Anyone have a similar issue?

 

[nissanh]

The brake lights taking a load. What other electronics are running at this time?

 

[470SNC]

At the time, just stock radio. When driving around locally, its totally fine which is the weird thing.

 

[Sandroad]

I suspect the testing was overly optimistic. Assuming the connections to/from the battery are clean and tight and the serpentine belt is driving the alternator ok, it seems likely the battery or alternator is bad. The voltage should never drop to 11.8, except when under starting load. It can be difficult to properly test a battery. Alternators are easier to test, provided they are out of the vehicle and not being affected by a bad battery. If it was me, I'd start by installing a new battery. If that doesn't fix it, then it's probably new alternator time (and you'll have a new battery to go with it!). There may be other possibilities for short circuits or other bad wiring, but those are real long shots compared to the much more likely usual culprits of battery/alternator.

 

[470SNC]

The battery is new, bought last November. It would be a shame to have to buy another battery instead of replacing this one under warranty if it is the battery. I suppose I should just replace the alternator anyway.