Alternator not charging

Your computer is registering a low voltage condition. You need to determine why you have low voltage. Either a bad battery, alternator that is not charging, or bad connection not allowing the alternator to charge. Your battery should have just over 12v and over 13.5v with the engine running. If you have proper voltage you need to see if the battery passes a load test. If your voltages are correct you need to look at your cable condition and connections.

If a check charging system message comes up then I would suggest you check your charging system... Meaning check to see if your alternator is putting out the right voltage and in most cases that would be about 13.5 volts.

Possible causes-- Low battery charge
- Battery defective
- Loose or missing alternator drive belt
- Faulty alternator
- Open or short system voltage circuit

Start by checking battery voltage.

Have the vehicle taken to one of many places that will test the Alternator output etc--narrow it down first without replacing that.

Voltage may drop enough to prevent starting without triggering the low voltage issue.

The car can start up and run but the battery light is on, is this correct? if this is correct then have the alternator and battery tested, you may have a bad alternator or battery, most of the time the battery light turns on when battery voltage is less than 12 volts and the alternator is not charging the battery above 12 volts, test alternator, the car will die out if the alternator is not charging the battery, the engine will run until the voltage in the battery gets to low and then the car will start to do funny things, if the computers in your car do not have the correct voltage they will send false readings and make the engine run bad and shut down. good day.

OK, the volt light means that the alternator is not charging the battery. It could mean the battery is shorted out, or the battery is bad or low on charge due to an alternator not charging.

Replace the Alternator and battery as indicated by standard voltage output tests under load.

The computer in the car will not operate the engine properly on low voltage.

Fixing the charging system, may resolve the rough idle (meaning that it may be trying to relearn after data was erased by low voltage of the battery), and the speed up.


Try the charging system first, and once that is repaired, reevaluate the engine driveability and speed and idle smoothness, after it relearns.

Good luck on this repair.

first check battery voltage. should be 12 volts or a little over. IF the battery is low then charge battery and then load test battery. If you remove you battery and take it to local parts store most will check for you. if battery load test good but was low on voltage then I would check to see that alternator is charging while engine is running. should be charging aprox 13.9 volts. if battery had full voltage and load tested good then most likely the starter is bad.

STARTING YOUR DIAGNOSIS
What happens when you attempt to start the engine? If nothing happens when you turn the key,"http://www.aa1car.com/library/2003/us20310.htm"to determine its state of charge. Many starters won't do a thing unless there is at least 10 volts available from the battery. A low battery does not necessarily mean the battery is the problem, though. The battery may have been run down by prolonged cranking while trying to start the engine. Or, the battery's low state of charge may be the result of a charging system problem. Either way, the battery needs to be recharged and tested.
If the battery is low, the next logical step might be to try starting the engine with another battery or a charger. If the engine cranks normally and roars to life, you can assume the problem was a dead battery, or a charging problem that allowed the battery to run down. If the battery accepts a charge and tests okay, checking the output of the charging system should help you identify any problems there.
A "http://www.aa1car.com/library/2002/cm10220.htm" that is working properly should produce a charging voltage of somewhere around 14 volts at idle with the lights and accessories off. When the engine is first started, the charging voltage should rise quickly to about two volts above base battery voltage, then taper off, leveling out at the specified voltage. The exact charging voltage will vary according to the battery's state of charge, the load on the electrical system, and temperature. The lower the temperature, the higher the charging voltage. The higher the temperature, the lower the charging voltage. The charging range for a typical alternator might be 13.9 to 14.4 volts at 80 degrees F, but increase to 14.9 to 15.8 volts at subzero temperatures.
If the charging system is not putting out the required voltage, is it the alternator or the regulator? Full fielding the alternator to bypass the regulator should tell you if it is working correctly. Or, take the alternator to a parts store and have it bench tested. If the charging voltage goes up when the regulator is bypassed, the problem is the regulator (or the engine computer in the case of computer-regulated systems). If there is no change in output voltage, the alternator is the culprit.
Many times one or more diodes in the alternator rectifier assembly will have failed, causing a drop in the unit's output. The alternator will still produce current, but not enough to keep the battery fully charged. This type of failure will show up on an oscilloscope as one or more missing humps in the alternator waveform. Most charging system analyzers can detect this type of problem.
thanks,please rate the solution positively.

Now change the sulfated batery for a new one.
Vitally

What initiated the need for jump starting? Is the alternator charging? Has the battery been checked?

To check the alternator, once the engine has been jumped and is running, remove one of the battery post connections. If the engine dies, the alternator is not charging the battery, and the symptoms you describe are the on-board computer going through low voltage spasms until sufficient electrical power to operate the engine / tranny is drained and the car dies.

If the car continues to run with no battery attached, the alternator is charging - - - and I would recommend removing the battery and having it checked and (if good) recharged to full capacity. I would also recommend having it charged even if the alternator is the problem just to delay the onset of the low voltage problems. The car should operate normally for a few miles before the battery drains too low after a full recharge, enabling you to get it to a shop for alternator service / replacement.

If you attempt replacing the alternator yourself, make sure the battery is disconnected prior to starting the job. Saves blowing up good stuff by accidental short.

Hope this helps and good luck!

-WB.