Car Died On The Road... Is It The Alternator?

milkyspit

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I need help from some of you auto guys on diagnosing a problem with my wife's car!
/ubbthreads/images/graemlins/help.gif

Last week my wife went out to her car, a 1990 Toyota Camry that's generally been running well, and it wouldn't start. Wouldn't even turn over. The strange thing is that it happened when she was at a local farmer's market getting some stuff... and when she had started the car to GO to the farmer's market maybe half an hour earlier, the engine started just fine!

She called me at work, and I instructed her to get a jump start from someone else in the parking lot. She did, drove home, and the car ran just fine.

When I got home, I measured the battery voltage with my DMM, and it read 12.58V. Then I started the car... started fine... and read the voltage again, with it presumably coming this time from the alternator... it read something around 13.8V. (I don't remember this particular number exactly.) I let the car idle for about 15 minutes, then shut it off and again measured the battery's voltage, which was around 13.02V, so I assumed things were working properly, as it seemed like the battery was slowly recharging as expected.

Today she called me again at work to tell me that the car DIED WHILE SHE WAS DRIVING IT. This is bad!!! She had the good sense to pull to the side of the road immediately, and fortunately for us a local architect came out to assist her. He jump started the car and followed her home to make sure it didn't die again en route. As he was leaving, he suggested that the alternator might be shot, mainly because the battery in the car is only a year old, is a very good battery... and because a bad battery wouldn't have started the car, but then caused it to die in the middle of driving.

I can add the following background information. About a year ago the battery we had in the car at that time "died" and was replaced by my uncle, who's generally an excellent mechanic. At the time he said the car still had its original alternator, but that it seemed to be functioning properly. However, about a year before THAT I replaced the PRIOR battery myself when THAT one had seemingly "died." So we're on our third battery in a 2-3 year span. Something ain't right, and IMHO it's not that we're buying crummy batteries! /ubbthreads/images/graemlins/mad.gif

This brings us to the inevitable questions: what's wrong, what should I replace, and how can I get it done as inexpensively as possible without sacrificing the quality of the repair? I'm guessing alternator for now, but does this history sound like the symptoms typical of a dying alternator? What do I do?

I'm pretty much an automobile engine newbie. If anyone can offer some advice to get me going in the right direction, please do!

/ubbthreads/images/graemlins/bowdown.gif /ubbthreads/images/graemlins/bowdown.gif
 

gadget_lover

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If the alternator is bad the battery will keep the car running for quite a while.

The fact that the battery read over 13 volts after driving it indicates that the alternator works at least some of the time.

As raggie said, if you disconnect the battery while the car is running the alternator should keep it running.

The sudden death would indicate a possible bad ground. I'd check where the battery cable grounds to the block as well as where the engine computer is grounded.

Other than that, I'd drive for a bit with a volt meter attached to the cig lighter outlet to see if the voltage is dropping suddenly at some point.

Voltage regulators can also make things interesting. /ubbthreads/images/graemlins/smile.gif

Daniel
 

Moat

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Alternator brushes will eventually wear out, and can charge intermittently towards the end - which could be your case (they may be replaceable, although often the slip rings and bearings will need attention too). I'd also give a real close look at ALL of the connections/junctions/cable ends (pos and neg) from the battery to chassis ground(s) and starter/fuse box/bus supply/etc. Like maybe check 'em for V drop across junctions while under load. Also might try driving the car with an accurate Voltmeter connected, to monitor any wild swings/drops.

I've always shied away from disconnecting the battery while running, as I've heard transient Voltage spikes can smoke the regulator (or worse)...???

My $0.02, Milky!


Edit - Ooof... Daniel beat me to it!
 

CiTY

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Alternators and water pumps, I would replace if they were over 100k as a rule of thumb. No need getting stranded...
 

Lurker

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Intermittent problems of "dead-- won't crank" can also be caused by a corroded battery terminal when the cable-to-terminal connection is weak.
 

dimwatt

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Milkyspit, Call some of the local auto parts stores. Most will test the battery and/or alternator for free. Stay away from most garages for this test as ineviteably, you battery AND alternator will be "bad"! (maybe your brakes too)

dimwatt
 

dimwatt

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Milkyspit, Call some of the local auto parts stores. Most will test the battery and/or alternator for free. Stay away from most garages for this test as ineviteably, you battery AND alternator will be "bad"! (maybe your brakes too)

Disconnecting the battery is a positive test but on newer vehicles can cause the alternator to fail, if it hadn't already.

dimwatt
 

Lurker

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If you disconnect the battery, the car will stall only if the alternator is not currently charging. If your alt is bad, it must be an intermittent problem or your battery would be dead in minutes. Therefore I wouldn't expect the test to work in your case.

Definitely get it checked out with proper diagnostic tools.
 

Zelandeth

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I had a car which did this a year or so ago. Would be driving fine, then just lose all electrical power without warning. Turned out to be a dodgy earth connection between the battery and the body.

I'd reccomend against disconnecting the battery with the engine running, given the level of the electronics in cars these days, I'd be seriously worried about frying something (Then again - I'm paranoid) I'd get it checked out by someone with the correct equipment.
 

juancho

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Milky,the same thing happened to me and it was a faulty negative coonection to the ground of the car, because that cable sneak out under the engine it is difficult to check.
If is that, do as I did and make the negative connection short and visible to a top part of the engine near the battery.
Juan C
 

Lynx_Arc

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I have had similar problems with a car awhile back. It could either be related to starting system or could also be electronic ignition module intermittent failure. The time it took to get jump started may allow it to cool down and be able to work. I had my car die while driving and wouldn't start right away then it got to where it took over an hour to cool off the module till it started. I noticed when I took off a plug wire that any electrical activity at all caused a spark at the plug when the key was in the igniton on position and not started/running.
 

BIGIRON

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My bet is simple problem with cables or connecters. Just make sure all connections are clean and tight. Don't forget that with age a cable can corrode and fail inside the sheath where it's not visible.

Sounds, from your testing, the alternators ok. I subscribe to the "don't disconnect the batt while engine running (and don't connect jumper cable when engine running) theory. No need to gamble many $$$ electrical parts.
 

greenlight

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My car died while I was driving. It was definitely the alternator. If you can get to it in the engine compartment, you can change it really easily. Or you might have to pull the engine.
 

Brock

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My money would be on a bad wire from the alternator or battery to the rest of the system.

I would strongly recommend not disconnecting the battery while the car is running; in newer cars this will damage computers and the like. In older car you will often get rapidly fluctuating voltage that can still cause damage. In really old car (maybe yours) it might be ok. In any case if the voltage rises while idling you have already ruled out the alternator. However it could be regulation of the alternator.

I would get a good voltmeter and see if you can watch it while running the car from the cig plug. Check to see if it sometimes quickly falls off (loose wire or bad regulator in the alt) and comes back up.

Just jumping the car wouldn't get enough power back in the battery for any real length of time, so it must be working sometimes. In any case I would charge the battery overnight to make sure it has a good charge on it, and if it stops again, check the battery voltage at the battery BEFORE jumping while trying to start. If the battery voltage drops really low the battery is shot, if it just sits there it is a bad wire.
 

BlindedByTheLite

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i just had to replace my alternator a couple months ago. it was going haywire and was draining brand new batteries within a day or two. replaced the alternator and everything's fine now.

also, as a new rule, i do not run ANYTHING in the car, not the radio/heat/lighter/headlights or anything if the engine is not also running. nothing drained the battery faster during my alternator problems than running something in the car with the engine off.
 

Minjin

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Testing the alternator without load is pointless. Go out with your multimeter and try again. This time watch the voltage and gradually turn on your lights, blower motor, radio, and rear defroster. Now you're actually testing the alternator. Engine might drop 50 rpms or so and voltage will go down, but it shouldn't sag below 13.5v or so.

If the alternator really did go bad, and she drove it till it shut off, the battery is probably shot. You should be able to test it and it might show 11 volts or something. Test it with load and it should be under 9 volts. Also, you didn't mention the incredibly obvious. If the alternator went bad, her battery light would have come on long before the car shut off. You can generally notice as things start shutting down as well. Many radios will turn off as voltage gets lower. The blower motor will get slower. These are all details that people should be noticing when they drive cars. For most people a car is the most complex machine they will ever own, yet they have no desire to learn anything about or observe the behavior of their own car.

It always amazed me when I worked as a mechanic how oblivious people are to problems. No, the car shouldn't be shuddering when you're accelerating from a stop. No, you shouldn't hear loud bangs every time you hit a bump or small pothole. No, you shouldn't have to turn the steering wheel half a turn before the car moves in that direction...

Mark
 

markdi

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do not forget about the ground connection to the frame or block of the engine - it could be bad - intermittant
 

DarkLight

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Dunno but when I replace my batteries and alternators I try to up the ratings as much as possible within reason....

I say check ground then have car diagnostics run..

computer controlled cars can be quite tricky..
 
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