takeabyte

Greetings all, long time lurker, first time posting. I am not a car expert by any means, but have been trying to learn little by little, building up my tool collection and using the info in these forums for working on smaller level projects. This post is for a 2010 Maxima (wife's car).

The car's battery voltage stays at around 13.0 V when in P, N, and D, and drops steadily while driving. The lowest I've seen it get after about 15 minutes driving near my home base has been 12.8V.

Shifting to reverse, the voltage shoots up to 14V and keeps steady at 13.8V - 14V, which is what I'd expect at all times when the car is on. The alternator was replaced about a year ago with a remanufactured one from Pep Boys by a trustworthy mechanic. The "new" alternator was already tested twice and is working to spec.

In-use voltages have been observed by one of those cup-holder USB chargers that reports the voltage at the port (not entirely accurate, but it has been within 1-2V when testing with a multi meter at the battery).

Backstory:
Two years ago, we were hit head on the drivers side quarter panel by an older lady trying to avoid someone backing out of a shop (video available for anyone interested in seeing it). Plenty of damage to the tune of ~$6k, about $1500 which was put in by us out of pocket (we stupidly claimed the accident to our insurance, instead of the lady's mandatory government insurance).

Several months later, the alternator went out on us and a friend-of-the-family mechanic replaced it with a remanufactured one from PB, which fixed the problem. Everything was sunshine and rainbows, but just over a year later, I was driving with the family and about 10 minutes into the drive, the battery and handbrake dash lights turned on, and the car sputtered while losing power a couple of times. Since this is the same thing that happened when our alternator went out the first time, I was able to get the car home and charged the battery over a couple days with a battery tender. We had the alternator tested, but it passed. We replaced the connector to the alternator since it was in severely bad shaped (it practically disintegrated when we pulled it out of the socket), but still seeing the same symptom, battery voltage drops steadily while using it, and jumps to normal charging when in reverse.

Hoping someone has any idea what could be the cause or tips on where to start - I've tried searching the forums here and Google but haven't been able to find anything useful over the past few days.

george1800

Based on the fact that you seem to be saying the charging system is operating normally when you put the car in reverse I would suspect a connection problem. When you shift in reverse the engine should move just slightly in the opposite direction compared to drive. This is flexing a connection someplace in your engine compartment. Take a look and move any and all wires around while the engine is in park and see if the charge kicks in. Be very careful around moving parts and report back with your findings. I would consider loosing and tightening all of your alternator connections as well. Something someplace is not connected well. Could even be on the firewall or inside of a wire that has broken wire strands. Let us know what happens!

takeabyte

Interesting thought! Watching the engine while another shifted, I noticed the engine does slump down just a bit. Just eyeballing it, I didn't see any wires getting tugged, but I'll need to take the radiator hose off to get a better look and start jiggling visible wires. We did notice a slight click in the engine bay when it was shifted from R to P, which I'm hoping is normal. It sounded like it was coming from the alternator's neighborhood.

Thanks very much for your input, and I'll report back soon as I give it a shot.

Richard66

Have you tried a new battery? Even if the existing battery tested good doesn't always make it good.

takeabyte

I'll try that first..I know with charging issues, you're supposed to start at the easiest thing, which would be battery. Will update soon hopefully.

MadMax07SL

I'm going to guess that despite test results, the alternator/voltage regulator are going to need to be replaced again. If it's not that, something else based on previous comment, could be faulty grounding. In my 07 Max years ago, I made my own grounding kit based on install instructions for a pre-made kit. I **** you not, after installing it, either 4 or 5 wires, re-established ground and everything worked much better, even the windows went up faster. So, grounding kit for 2010 could make it for about $25 worth of parts, and see if that gets you going. Quicker to install then a new alternator. The other thing, and this is just an aside, I'd always go with a new alternator or starter over a rebuilt. Too many things can go wrong, and it's a lot of labor to get to those parts...not worth the money saved.