Parasitic (or ignition key off) drain is the cumulative load produced by electrical devices, for example, emissions computers, clocks, security alarms, radio presets, etc., that operate continuously after the engine is stopped and the ignition key has been switched off. Normal parasitic loads are below 75 milliamps (.075 amps). When the parasitic load is greater than 75 milliamps (.075 amps), batteries will drain more quickly. Glove box, trunk, and under hood lights that do not automatically turn off when the door is closed or shorted diodes in alternators are the most common offenders. Cooling fans, power seat belt retractors, radios and dome lights left on, alarm systems, and electric car antennas have also caused batteries to drain overnight. Leaving your headlights on will generally discharge a fully charged car battery, with 90 minutes of Reserve Capacity (36 amp hours), within a couple of hours. It is highly recommended, especially if you are using a sealed wet "Maintenance Free" (Ca/Ca) battery, allow to thaw if frozen, fully recharge it in a well ventilated area with an external battery charger, remove the surface charge, and load tested both the battery and the charging system for latent damage from the deep discharge. You could have a damaged or bad battery. If the alternator is warm and the engine is cold, then check for a shorted diode in the alternator. Below are some methods that are used to test the parasitic load with the engine NOT running, under hood light disconnected, all accessories switched off, and the vehicle doors closed: * Connect a 12-volt bulb across the positive and negative battery terminals to test the bulb and the battery. If it glows brightly, then remove the negative battery cable and connect the bulb in series between the negative battery cable terminal clamp and the negative battery terminal. If the bulb continues to glow brightly, then start removing fuses or connections to the positive battery post one-at-a-time until the offending electrical component is identified by the bulb dimming. * A better approach is to use a DC ammeter, for example a Fluke 175, inserted in series with the negative battery cable terminal clamp and the negative battery terminal or a clamp-on DC ammeter, like a Fluke 336 or i410 around the negative battery cable. Starting with the highest scale, determine the current load. If the load is above 75 milliamps (.075 amps) after the initial surge, then start removing fuses or connections to the positive battery post one-at-a-time until the offending electrical component is identified by the parasitic load dropping to within 75 milliamps (.75 amps). ADDED 25-APR-06 BY Guycaron: For whatever it's worth, this problem came up in both my '86 LSC and '91 LSC/SE. The quick solution was a new voltage regulator. Cheap, easy to replace. Worked both times.
either the alternator or the voltage regulator are no good.may also be a bad battery
Your battery is weak, or your your alternator is not charging battery.
Failed battery, or alternator is overcharging.
poss alternator fault
Can be loose or corroded battery connections, loose drive belt, or the alternator is failing.
Alternator is defective and needs replacing.
The positive cable between the alternator and the battery has an open circuit or break. There also is a set of wires that plug into the alternator that turns it on when the car is running. Wiring problems here can cause a alternator not to charge on the vehicle but works fine on a test stand. Some cars the alternator light in the dash causes the alternator to kick in when the engine is started. A burned out light in the dash causes the alternator not to charge.
It's not charging the battery. Check the alternator.
i think you are having problem with your alternator its not charging your battery
could be a bad battery
The most common reason for a vehicle not to turn over is a bad alternator. If the alternator is not charging the battery the engine will not start, regardless of the battery age.
A few causes that will make the Battery Light come on are: 1. Faulty Battery 2. Loose Battery Connection 3. Battery is not Charging, ie. Faulty Alternator
Defective alternator or voltage regulator. Also possibly the battery is defective with a dead cell.
weak battery or bad alternator.
A failing alternator.
Yes, alternators are designed to maintain the battery, or recharge a battery that has been slightly discharged from starting the car. When the alternator is used to recharge a dead battery, it causes the alternator work harder and longer than it is designed for, causing it to overheat, thus causing damage to the alternator. A battery charger should be used instead. They are designed for charging dead batteries. After the battery is charged, let the alternator maintain the charge.
it means your battery isn't charging from the alternator, could be a fault either with the alternator or your aux drive belt maybe snapped is the most likely causes
The main cause of battery drains is a bad electrical system. The electrical system is normally powered by the alternator and once the alternator goes bad the battery has a hard time holding a charge,
The battery light usually comes on if there is a charging system problem Either battery or alternator are the usual causes.
the common cause why the light is on is that your alternator is not working well,try to have your alternator checked .may be the carbon brush is already worn out.
chances are it's the voltage regulatorit could also be a wire no connected on the alternator
A bad voltage regulator in the alternator. Depending on year make and model it may be outside or separate from the alternator.
A bad alternator will not give proper power to the vehicle. Dim lights, buzz in the stereo or a dead battery could all be causes of a bad alternator.
Overcharging. Check your electrical system to see if the alternator is overcharging the battery. It can also be the battery is defective and needs replacing.
I'm not sure about all of these, but I have a 98 Taurus and the battery light came on. After a few days, the car died altogether and I had to replace my alternator. I would definitely take the battery indicator seriously and have your alternator checked.