How accurate is this dashboard light?

September 26, 2008 11:38 AM

The "battery not charging" light on my dash went on; the mechanic told me I need a new alternator. Now the "battery not charging" light has turned itself off again. Does this mean my battery is, in fact, charging?

After a couple-of-thousand-mile road trip, I left my mid-90's Honda Civic unused for a few weeks. When I started it again, the "battery not charging" light on the dash was on. Two different mechanics concluded that the alternator was shot (I went for a second opinion, since I just had the alternator replaced last year.) I opted not to replace it immediately, and on the drive home the "battery not charging" light went off again.

Could this mean something that came loose in the alternator has temporarily shaken itself back into place? I know the alternator probably still needs replacing, but I'm wondering if I can safely use the car for short trips until/unless the battery light comes on again.

Extra bonus question: how long can I put off replacing the alternator if I get a solar trickle charger?

posted by fermion to travel & transportation (6 answers total)

It's not just the light. Your mechanic should check the output voltage of the alternator. If its low, it probably needs to be changed.

An alternator charges while you are driving, a trickle charger won't do anything.
posted by wongcorgi at 12:03 PM on September 26, 2008

Couple of thoughts based on cars I've had:
- Many auto parts places can do a quick test on the alternator to determine if it's working properly, although it does require yanking it out of the car
- The main ground connection(s) may be loose or corroded
- The battery may be going, not holding a charge
posted by hungrysquirrels at 12:11 PM on September 26, 2008

Head over to an Auto Zone and they will check out your electrical system components -- battery, alternator, starter, voltage regulator (if you have one on this car, whatever else they recommend you check. If you don't know your way around a wrench, go with a friend who does, so he or she can help the guys in this process, even if it's just holding a pair of pliers and looking alert.

Changing out a battery is easy, and I've seen the guys at Auto Zone do it for customers. An alternator is not so easy, depending upon the design of the motor, how it is laid out, and I don't think you're going to get the guy to help you on this one, though they are extremely helpful as far as information ("Oh, no; the rimforator sprocket must be removed before the left-handed pull-grindle. And always back out the pinder loop first thing.") and will loan you a few tools if you need them.

Er, on review, thinking about it for a few minutes -- Sears automotive used to do this sort of electrical check for maybe ten or fifteen bucks, and that money taken out of the total if they do the work to repair the vehicle, and I've had good luck with them, with a nationwide warranty and a reasonable price; you might want to check with them first. Call them, see if they still offer this, etc and etc.

Mechanics will tell you anything -- anything -- and unless you have solid information you're stuck believing them, which can cost you a lot.

Last. Sometimes lights are bullshit, things can go wrong with warning systems, same as anything else. If everything checks out fine and the light is still on, cover it with a piece of tape and rock on down the road..
posted by dancestoblue at 12:52 PM on September 26, 2008

You are right dancestoblue . Sears will do an electrical system test to see iof its the battery or the alternator. I think the test is free if it ends up that something has to be replaced.


Sears was very good when my car had similiar problems. (turned out to be a dying battery ).
posted by majortom1981 at 1:57 PM on September 26, 2008

How old is your battery? If it's four years or more, replace it on general principles and see if the fault goes away.
posted by flabdablet at 8:15 PM on September 26, 2008

It could be that your alternator belt got real wet and was slipping, and the alternator was not rotating to generate a current. Now the belt is getting traction again and all is well. It also could be that a bearing in the alternator is starting to sieze up, but hasn't completely done so yet. Typically, though, you would've heard the belt slipping as a loud squealing sound.

Extra bonus question: how long can I put off replacing the alternator if I get a solar trickle charger?

Hard to say, but this is not ideal for one reason: automotive batteries are not "deep cycle" batteries. This means they're not intended to be discharged significantly and recharged many times. Just a few times of running the battery all the way down may kill it. A car battery is intended to start your engine, and that's about it. If you were feeling creative, you could get a marine deep cycle battery and experiment with that kind of thing, but it would probably cost more than a new alternator.

Anyway, since the light has gone out, and the car is apparently still running fine (?), I would probably not take any action until some sign of a problem returns.
posted by knave at 8:22 PM on September 26, 2008