After jump starting, my engine runs fine. I thought maybe the battery needed to be charged. So, I let my car run for 30 min. I, then, turned the engine off and started it again. It started OK. But an hour later, when I tried again, the engine won't start again. There is no sound coming from the battery at all. It is completely dead. The same problem happened 6 months ago. I cleaned the terminals and my car was fine until now. I cleaned the terminal again, but this time, it doesn't solve the problem.
Could it be the battery or alternator? My battery is 3 years old. My alternator is 7 years old (driven 50K miles after replacing to this one). I only drive maybe one mile a week just to go stores. I am not sure if the problem is caused by my driving habit (so little), battery or alternator?
I don't want to replace the battery if that's not the cause. I cannot afford taking my car to a repair shop. I'm hoping I can take care of the issue on my own…
Could someone help me identify what the problem might be?
Thank you very much.
Suggestion:
First off, let's see if it is your Alternator. Try this:
The electrical system in an automobile is said to be a 12 volt system, but this is slightly misleading. The charging system in most cars will generally produce a voltage between 13.5 and 14.4 volts while the engine is running. It has to generate more voltage than the battery's rated voltage to overcome the internal resistance of the battery. This may seem strange, but the current needed to recharge the battery would not flow at all if the charging system's output voltage was the same as the battery voltage. A greater difference of potential (voltage) between the battery's voltage and the alternator's output voltage will provide a faster charging rate.
As long as the engine is running, all of the power for the accessories is delivered by the alternator. The battery is actually a load on the charging system. The only time that the battery would supply power with the engine running is when the current capacity of the alternator is exceeded or when engine is at a very low idle.
If that test shows your Alternator is okay, take your battery to an auto parts store and have them check it for a dead cell.
Just read another "answer" to your problem. The answer advised you to remove the positive battery cable while the car is running. If the car remains running, then your Alternator is alright.
That little trick worked on the older cars, but NOT on today's modern engines with all the electronics.
Some people tell you that you can check your alternator by disconnecting it from the battery to see if the alternator can produce enough current to keep the engine running. Disconnecting the battery will subject the voltage regulator (and computer and audio equipment…) to significant voltage spikes which may cause an otherwise good alternator to fail. Even if there were no damaging spikes, this test would not indicate whether or not the alternator was good because the engine will easily run with a weak or failing alternator.
{ 3 comments… read them below or add one }
sounds like a battery to me, if it will run with the battery cable disconnected then the alt is fine.
It is most likely a battery problem, I would recommend maybe checking the power of the battery with and electrical power measurement (commonly used to measure house hold battery power) to see if there is power. If there is power you need to get the wires replaced running from the battery to the central circuit board (just manages the current and distributes it where necessary) I would also recommend replacing the wiring in the distributer cap. If there isn't power replace the battery. Most of this does however require a repair garage unless you have extensive knowledge of both cars and electrics.
If you don't have an inexpensive volt meter to check the battery voltage, any car dealership, auto-parts or battery store can do a free *load test on your battery to check the reserve capacity. If you have an inexpensive battery with a short warranty period most likely you have a cell that's shorting out at the bottom.
If you have a store near you who still sells your brand of battery they should pro-rate the months of use toward a new battery.
The really sweet part about a volt meter is you not only can check the battery voltage with the motor off (12.85) leave it hooked to the battery with the car running to check alternator output (13.5 – 14.0) volts.
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