Alternator or battery?
June 1, 2011 5:54 AM   Subscribe

Battery or Alternator? Clues inside.

My car is clicks repeatedly when I turn the key, but it doesn't start. Can you tell whether it's the alternator or the battery based on these details, or others you could ask me?
1. It happened a few days ago, too, but then started on the third try.
2. My clock's : is still flashing, but the time is no longer right.
3. The little light in my AC button flashes while the car clicks.
4. The coolant looks very low.

It's a Subaru Legacy, 2002. I'm not at all knowledgable about cars, but the repair place said they could fix it quickly if it's the battery, but that it would take a while if it's the alternator. I'm currently waiting for roadside assistance to come give me a jump or tow.
posted by daisyace to Travel & Transportation (14 answers total)
Best answer: 1. It happened a few days ago, too, but then started on the third try.

"It"? What actually occurred? Or did you just go outside one morning to get in your car and it would only click? Describe the situation that occurred, if you happened to be there, it might help.

Usually when an alternator dies you'll know it. you'll see your battery light (i know it's confusing) come on and the car will lose power, sometimes immediately, sometimes you can run on the battery for a good while before it coasts to a stop.
posted by zombieApoc at 6:02 AM on June 1, 2011

Best answer: If your car clicks and won't start, there is not enough charge getting to the starter motor to turn over and start the engine. Coolant is irrelevant. Coolant only produces cooling problems.

1. This leads me to suspect the battery is either flat, or there is a loose connection. When it started on the third try, was it fast (ie *chugga-chugga-chugga-broom*, like normal) or *chu....chu.....chu........chu..broom!*

If it's the first one, then check the terminals on top of the battery. They may need cleaning or tightening. If they are fine, then checking the other end of those cables, the starter motor connections and the main earth is required (which sounds well out of your league at that stage).

If the second, slow start, option is how it went, then you may just need a new battery.
posted by Brockles at 6:02 AM on June 1, 2011

It could also be the Starter.
posted by zombieApoc at 6:03 AM on June 1, 2011

How old is the battery? If you jump the car does it start?
posted by majortom1981 at 6:03 AM on June 1, 2011

PS if you bring it to say sears to get a battery they will do an alternator test for free before replacing the battery. Other mechanics should do this also.
posted by majortom1981 at 6:04 AM on June 1, 2011

Hopefully my awesome onomatopoeic explanations aren't too technical and help you!
posted by Brockles at 6:04 AM on June 1, 2011

Best answer: For those suggesting the start, yes normally it's a possibility, but the fact that the clock has lost the time suggests strongly that the power has been lost to the car either before during or after the start attempt, so at some stage, the battery was either really low (ie when cranking) or lost connection (if it's a loose wire).

It's unlikely the starter could do that as it failed.
posted by Brockles at 6:06 AM on June 1, 2011

Response by poster: Thanks all, it looks to be a partially broken cable, according to roadside assistance.
posted by daisyace at 6:08 AM on June 1, 2011

The first way of diagnosing this problem is by jumping. Does the car keep running after the start? If, after say, an hour, of running, if you shut off the car and it fails to start again? That's the battery. If it dies while running, it's almost always the alternator.

These aren't always true, but account for the vast number of electrical problems.
posted by General Malaise at 6:09 AM on June 1, 2011

Best answer: I was going to suggest a bad cable or bad ground. (Really! I was!) I had a garage replace the alternator on a car once (their diagnosis). It was very expensive and futile. The problem turned out to be a corroded ground strap between the engine and the chassis.

Tip: Always wash your hands after touching a battery or battery-cable terminals. I'm talking about a thorough wash using soap and plenty of water. Do not touch your clothes until you do. Battery acid will eat holes in your favorite jeans if you wipe your hands on them after handling a car battery, and you won't know it until they come out of the wash.
posted by Kirth Gerson at 6:26 AM on June 1, 2011

Another thing to check is the serpentine belt. Easy to overlook and causes the alternator to stop spinning.
posted by PSB at 6:51 AM on June 1, 2011

My lawn tractor did this last week: "tick-tick, tick-tick, tick-ticka." Noooooo!

I know the battery was full because I hooked it up to a charger, so I grabbed a file and went to work on the battery terminals and the ends of the cables. Once those were clean down to fresh metal, I blew away the filings and hooked it up -- and it started fine.

Wear eye protection. Don't tip the battery. Don't open the battery. Wash your hands after touching the battery. Don't touch your eyes, nose, mouth, or skin after touching the battery. Don't discuss religion or politics near the battery.
posted by wenestvedt at 7:32 AM on June 1, 2011

Autozone will run the alt/battery test for you as well. If the cable was damaged for long, you might have to replace one or both of them soon. Make sure you get it tested; irregular charging/draw cycles can cause premature wear on the battery, which in turn can damage the alternator.

Sometimes you can get alternators repaired at fleet-shops. It's a lot cheaper than buying a fresh alternator.
posted by thsmchnekllsfascists at 10:58 AM on June 1, 2011

These two items are not mutually exclusive and quite often go bad together. It it is the original alternator it is probably due to be replaced and as these two components work very closely together one going bad can make the other go bad (skips long technical discussion as to why). Get them both tested and replace as needed. Sears can do it as can most independant mechanic shops. An easy test is once the car is running turn on every electric device the car has, if the lights are dim or the horn sounds weak it is probably the alternator, and definately the alternator if it dies. These tests are really only valid with a known good battery. An easy way to get a known good battery is to take one out of car that is running, or buy a new battery and install it. Good luck.
posted by bartonlong at 11:57 AM on June 1, 2011

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