Starting problems, could it be something other than the battery or alternator in this case?

Question

Vehicle of interest is a 2010 Dodge Charger.  This issue involves a co-worker whom asked me advice a while back on what could be wrong with her car.  The symptoms described an obvious failing alternator.  She'd also mentioned that it had been a problem getting progressively worse for several weeks.  After the alternator replacement, all of the symptoms cleared and everything was fine.  I also warned her to keep an eye on her battery performance, considering the length of time that her alternator was failing.  All was well for 2-3 weeks.  Then she started having intermittent trouble with starting the vehicle.  Sometimes it clicks, no start.  Sometimes it starts but after a lot of cranking.  I directed another co-worker to attach jumper cables directly to her battery (in the trunk) one night recently because it wouldn't start; the relay would just click.  Apparently, it started and maintained idle but she detached the cables very quickly and it immediately died.  They came to me and I told them to do it again but this time, keep them attached with her car idling for much longer.  It must have been a good 20 minutes, at least, and after detaching, it once again died, but this time it sputtered heavily first (I wasn't there, this was explained to me).  I didn't have a multimeter on me, but I personally checked the connections for corrosion and tightness and both checked out fine.  The terminals were very clean and the cables were tight.  I told her that, in my opinion, it must be the refurbished alternator or the battery. 

But I take it to the community here: Could there be anything else I just haven't thought of, considering the events that took place?  Apparently, the next morning, it miraculously started and she went to an auto parts store to have both the battery and alternator tested.  They both tested out fine.  It still seems like it necessarily must be one of the two.  What do you guys think?

Answer 1

Sounds like a couple of things are of concern. The motor should run with a low/dead battery and the alternator should provide for most electrical demands, so I would suspect the alternator, new or not doesn't matter, I have gotten brand new bad parts.

Second, the car may have a large enough drain on the battery to deplete it, possible trunk, glove compartment and/or interior lights would be where I would start.

Answer 2

In a situation like this, I always verify clean battery connections, and I verify the grounding of the battery.

As an example, on a VW TDI (diesel) someone complained of good starting when cold and poor starting when hot. They had a thermostat replaced about 4 weeks before this. She got stranded several times, and once I was called to help. When I got to the car, I did my normal practice of a jumper on the battery and a jumper on a flange on the cylinder head. The car started. But it died on the road. Again, I got it started.

It turned out that someone loosened a 13mm nut holding the - cable from the battery to the transmission bell housing. Funny how that would happen!

It also adversely impacted charging the battery.

Harbor Freight gives away voltmeters, and every car should have one in a secret compartment.

Check out the grounding. There could be a bad battery. In my area Autozone and Advanced Auto test batteries and alternator function on the car. Perhaps that might help. If performance is changing, look for poor electrical connections, as it is the most probable cause.

There could be other causes, but this needs to be resolved first. Otherwise you could throw a new battery at it, and that might not be the problem either.