... left the car at my apt for about 1.5 weeks while I was home for the holidays. Came back, it wouldn't start up... got a jump, started OK, but noticed that there was a little corrosion on the positive terminal of the battery. (Previous to all of this, I'd been having problems with the car not starting up, which had turned out to be that the connection to the battery posts was loose-- my mechanic tightened up for me, and worked fine after that.) Didn't think much of this, kept driving, planning to call the mechanic about it.

Today again it wouldn't start up but did respond to the jump, and I did have a better look at the corrosion. It's a bluish-white salt around the positive battery terminal. From what I've Googled so far, it seems this is something you can take care of yourself, with some tools, a wire brush, and maybe some baking soda? I spoke with the mechanic today, he seemed to think so, and that battery replacement is likely not necessary? (The battery is only 2.5 years old... had to be replaced when I first moved down here.) What do you guys think?

TiA

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Freya says, 'Hello from NOLA, baby!' (Laissez bon temps rouler!)

Only 2.5 years old? I'll grant that this is not that old, but that's the first place I'd look - is the regulator and alternator working? Maybe it's just not charging.

PizzaGod, all of that should have been fine-- from the last time I brought it to the mechanic, and it was running fine (that was a few weeks before the holidays).

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Freya says, 'Hello from NOLA, baby!' (Laissez bon temps rouler!)

It would be good to get rid of the corrosion but if you want to eliminate it as a possible cause of your current problems, all you have to do is loosen the terminal clamp bolts a bit, work the clamps back and forth a bit, and tighten.

If you can start a few more times after driving, it's probably not the alternator or the voltage regulator.
I would also suspect the battery at this point-- you might have been dealt a dud.

If you're dealing with unusual humidity there could be other electrical system problems, e.g. distributor coil, old/bad spark plug wires.
What kind of car?

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[www.papanicholas.com]

Here's another thing to consider. The alternator system on todays cars is really not a "charger" but a "maintainer" Rather it's job is to replace the electricity the car uses but not necessarily bring a dead battery back to life in day to day use. I would suggest taking off the terminals, cleaning the battery using copious amounts of water and baking soda (to avoid moving that corrosive stuff from the battery down onto the inner fenders and starting new problems). Then, with a stiff wire brush or even a jacknife, shine up the terminal posts and the inside of the cable clamp and tighten them down.

Now get it started and drive somewhere to get the battery recharged and tested or, if you have a friend with a trickle charger and a garage, connect the trickle charger and let it charge at least overnight or better, for a day or two.

A quick and dirty test of the alternator (best performed at night) is to start the car, turn on the headlights and any other electrical loads - heater fan, A/C, rear defogger and slowly bring up the engine speed. If the alternator is working, the lights should get brighter as the engine speed increases. If you have a volt meter, connect it across the battery in DC Volts mode. With the engine running at a couple thousand RPMs you should see 13.8 to 14.4 volts if all is well. This number may be influenced by the discharged battery.

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If the terminal connections are truly tight, "a little corrosion" won't be a problem. However, you can't see from the outside the corrosion that matters, between the battery post and the inside of the cable's terminal, i.e. where the two actually make contact. Have to remove the cable from the battery and examine.

Do the wire brush baking soda routine. Make sure you scrub on the inside of the cable terminal. When done tightening the cable, you should not be able to rotate the terminal on the post by hand. Don't freak out if you find yourself tightening it so much the tips of the terminal begin to bend and meet --- the terminal is made of soft metal, it won't break.

Quote
olnacl

A quick and dirty test of the alternator (best performed at night) is to start the car, turn on the headlights and any other electrical loads - heater fan, A/C, rear defogger and slowly bring up the engine speed. If the alternator is working, the lights should get brighter as the engine speed increases.

May I append this? I'd expect the lower voltage reading only at idle, and only on some cars. Immediately above idle and essentially at any higher RPM I'd expect the higher voltage reading to be constant if the regulator's job is being done.

Append to the append: Deckeda is correct although I might disagree with the "immediately" part of the above idle statement. Anyway, the append: Higher voltage readings (and we don't even know if you have a volt meter handy) generally above 15 volts may indicate either a faulty regulator or a sulfated battery that's due for replacement.

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take the cable off, clean the cable end and battery post with a strong baking soda/water solution until all the bubbling stops. then take your $2 battery terminal cleaner brush and clean the post and inside the cable end. If you want to get a tube of anti-corrosion jelly stuff from the auto parts store at the same time as you get the brush, use some, then put it back together.

The battery may have a wee bit of acid seeping between the plastic case and the lead terminal. It happens. As the battery charges it generates hydrogen gas, and if the vents aren't up to the task, it may find its way past the terminal if the seal isn't really good. I doubt the charging system is at fault. The corrosion build-up is worse between the post and cable clamp, and it has a much higher electrical resistance. Alternators don't do so well if there is a high electrical resistance in the system.

Loose connections on battery cables can cause all sorts of wierd problems.

Clean with baking soda.

Then coat with grease/anti-corrosion stuff. Actually Vaseline works really well here - just cover the exposed metal portions of the terminals with a layer of the stuff.

I always keep the battery clean and the connections brushed. That's the problem 95% of the time.

Although at 2 1/2 years a bad battery isn't unusual. I just replaced a bad one 2 weeks ago that was only 3 years old. It was an 84 month battery. I got 50% off the new one. Take it down to the place you bought it and they will charge and test it.

I haven't had to pay full price for one in years.

I wouldn't think twice about replacing it now. What is it, less than $75 bucks?

What RacerX said. BTW, here is a picture of the battery terminal cleaning brush that he was talking about. I have one and they work really well and are much quicker than "make do" implements.

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Roswell, GA (Atlanta suburb)

That is the right brush for the post type terminals, it is different if you have a side terminal battery.

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Thanks all, I will print out this thread and have a look at it over the weekend.

While you all were posting this, in the meantime, I had read a "quick and dirty" way to get rid of the corrosion, which I tried and it seemed to work... Coke (Diet, that is)...

Will deal with this more over the weekend, when I have a bit more time...

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Freya says, 'Hello from NOLA, baby!' (Laissez bon temps rouler!)