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Car advice....
blaisepascal
This morning skitten went to start the car, and it failed to do anything. I wasn't there, so I don't know exactly what the symptoms were, but she was unable to go anywhere today.

This evening (minutes ago, in fact), I tried it. I got no click, no lights, nothing. My VOM shewed 2.88V across the battery terminals, rather than the expected 12V.

Does this seem like something that can be fixed with a jump, or is a new battery necessary?

ETA: I've pulled the battery, and the resistance through the car from POS to NEG is about 67Ω. At 12V, that would work out to about 180mA. I figure that could be the clock in the radio.

The battery is now in our front hallway, warming up. I doubt it'll help, but I can take it with me to the parts store tomorrow without a problem.

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You know there are three possibilities:

1) Someone left something on so the battery drained down. A jump will fix this.

2) There battery has ceased to hold a charge. New battery.

3) A short has developed in your electrical system. You'll know that that is the case if you get a new battery and it dies within two days. :-\

So you have no real opinion on whether a jump will fix it or not?

I though kinnerc was clear: There is a 1 in 3 chance a jump will fix it.

That's making the unjustified assumption that all three possibilities are equally probable. If they aren't, then it's not necessarily a 1 in 3 chance a jump will fix it.

Would you be willing to drive skitten and I around tomorrow morning to get a new battery? I can't get you on the phone.

True.

I suspect that statistically there is more than a 1 in 3 chance that something was left on and all you need is a jump. After that, considering the temp outside, the second most likely cause was a weak battery and the cold. the least likely problem (of the three) is a short.

But still I wouldn't buy a new battery untill I was sure I needed one. I had this exact same problem at Thanksgiving. Ever since the neighbors gave my car a jump it has been running fine.

What time do you want me to come down?

I think it is the first thing to try, karulo. I think you have a slightly better than 70% chance it'll fix the problem.

tom thinks it's a new battery
and if it is then we a) need to useAAA rto get the car to the shop & b) grt duane to fux it... and maybe buy a charger?

Here's one way to tell, if you have a 10 amp battery charger.

Check the cells and verify they have a proper amount of water (if its not a sealed battery). Put charger on and leave overnight.
Check charge rate in the morning. If charge rate is reasonable (a couple amps) and the voltage after removing the charger is good, and the car can start, you dont need a new battery. (A battery hydrometer check would be more helpful. Again, if not a sealed battery. Look for a green eye on a sealed one.)

If any of the above is not true, you do. But keep an eye on things for a few days. If it appears that the battery is not staying well charged, then you do need a new battery.

The other question is, how old is the battery and has it ever given any trouble before?

Jumps dont fix anything btw... They just get you home after a problem.

I don't have a 10 amp battery charger; the battery is 30 months old, Exite brand. I thought it was sealed, but it looks like it might not be. I'm not sure I can open it to check the water level.

We have a door which hasn't been closing properly, so the "door ajar" idiot light has been usually on, but I dealt with that situation a couple of days ago. I don't think anything else was on that would have drained the battery.

It has been having a starting issue, where initially the starter would spin but not engage the flywheel the first one or two times we turned the key. I didn't think that was a battery issue.

My next trick is to remove one of the battery connectors and check the resistance from hot to ground. That should show if there is any drain.

2.5 yrs shouldnt be too old. but I see you're in cold country. Whats the cold cranks? On the plus side, 30 months may mean you're still under a pro-rated warranty.

A door light might draw enough to be a problem if the car was parked for several days. Overnight it shouldnt make a huge difference unless the battery was weak to begin with. (Dome light is an amp or two per hour)

Your starter sounds like a mixed signal. Not engaging the solenoid could mean the battery was weak. Or it could mean the starter is wearing out. Alas its not definitive either way without knowing more.

Modern cars always have a slight drain. If you have an amp meter setting for 10A, measure the amps draw with everything turned off and doors closed. (Inline on the plus wire, NOT to ground). Expect a low fraction of an amp (unless you have a hood light, in which case, add that in, and make sure its going out)

Has the car been run a lot lately with a heavy electrical load? (IOW, drawing more than the alternator can put out? EG headlights, defoggers, defrosters, and idling engine) That can slowly drain a batter over a few days driving.

Unless you know your alternator is doing well, I'm starting to suspect you'll want to check it too. It may be that its a bit weak and not keeping the battery up. Check your volts when running under light and heavy loads to see if it needs a load test.

Oh, and I gather you've checked your battery terminal cleanliness. Its amazing how little corrosion it takes to foul up an electrical system.

Obviously right now the cold cranks is 0A, but the rated CCA is 525A@0°F. I have no warrantee information and have no idea where to go. We got the car used, and the battery was in it when we got it. The dome light wasn't on, but a dashboard idiot light might have been. Like I said, it's been on overnight before recently in even colder weather and the battery hasn't been dead.

I was unaware until I just checked Wikipedia that starters no longer use a Bendix drive, and that they have a separate solenoid for engaging the drive pinion. That forces me to re-evaluate the starter. Rats.

According to Wikipedia, the room temperature open circuit voltage for a car battery should be around 11.8V for a battery with 0% charge. I measured 2.88V. Granted, the battery temperature was around 12°F, but that still seemed excessively low.



Oh yeah... who are you? I don't like anonymous comments in my journal. Use a pseudonym, fine. Post "anonymously" because you don't have an LJ, but sign it, fine. But posting anonymously and not signing, not so fine to me.

My first guess is that your alternator is shot. If it gives no juice, it means that there's no battery-borne signal. I've had this happen before, and while there's many things that could go wrong with an electrical system, I'd would first ask about an alternator replacement - $350 or so incl labor - and then go from there.

in order of likelihood, the possible problems are:

1. discharged battery. a jump-start will enable you to get the car running, but you have to remember that the battery still needs to be recharged. that means driving the car (not just sitting with the engine running at idle!) for at least 15 minutes (and an hour is better), without turning on the headlights, heating/cooling fan, windshield wiper/washer, power windows, or radio.

2. totally dead battery, which will not take or hold a charge. the fix for this is to buy a new battery.

3. malfunctioning alternator and/or voltage regulator - these are often combined into one physical unit. it's very difficult to check these with common geek tools, so take it to a repair guy. has the "alternator/battery" idiot light been coming on more often recently? sometimes it's just a matter of adjusting the belt that drives the alternator (if it's loose, the alternator won't provide enough power to properly charge the battery).

4. other electrical problem. automotive electrical problems can be infuriatingly difficult to diagnose. you'd think a simple DC circuit would be pretty straightforward... but it isn't. again, take it to a professional who has the specialized equipment to deal with it.




If you can get a friend to jump the car, and you're willing to take the risk of the car dying again somewhere else because there was actually another problem, then I think you should jump the car and see how it goes. This has been my course of action in this situation. Sometimes it works, sometimes it doesn't, but it's an easy and cheap thing to try, so usually worth a shot.

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