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How do you check the alternator on your 1993 BMW 325I and could a bad alternator cause a current draw battery goes dead with the car off battery load tested ok voltage is 12 with car running?
Wiki User
∙ 16y ago
Voltage should be 13 to 14.5 with car running. Sounds like the diode pack. If theres a big plug on the back of the alternator, disconnect it overnight. Reconnect before you try to start the car (a label on the steering wheel might help you remember). If the battery is flat you need to look elsewhere.
Wiki User
∙ 16y ago
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How does an alternator produce different amps?
It depends on the load and the voltage. In an automobile, a battery will typically have a voltage of about 12 Volts. If the engine is not running and you turn on the lights, the lights will start drawing current from the battery and the voltage will drop by a volt or so, depending on how strong a charge the battery has. An alternator will produce in the neighborhood of 15 Volts. If it is trying to push current into a system with a fully charged battery, it will only be able to push a few amps. If the voltage in the battery drops, the alternator will be able to push more amps. A completely dead battery will draw the most current (amps).
Why is the car battery charging at 14 volts running and 13.5 not running?
your alternator charges the battery while the car is running. The alternator actually puts out a higher voltage than 14 volts while it is running, but it is reduced by a voltage regulator (most of which are already built into the alternator housing), to prevent damage and premature death of the vehicles battery. While your car is not running, the alternator is not charging the battery, and the 13.5 volt reading you get is just the measurement of the voltage the battery is holding at that given point.
Can a car's alternator charge the battery while the car is not running?
No. The alternator has to be turning to produce the charging voltage. It only turns when the engine is running.
Do you need a voltage regulator if you have an alternator?
yes to regulate the current before it in to the battery.
How does an alternator keep a cars battery charged?
An alternator has diodes which transform ac voltage to dc voltage so that the battery gets negative and positive current on its poles thus making the battery to be charged.
Can running a new alternator on a half charged battery cause damage to either the battery new alternator voltage regulator etc?
Not likely, but running the engine with a dead battery can damage some alternators. Always fully charge the battery when installing an alternator.
What charges the car's battery?
The battery is constantly being charged by the alternator as long as the engine is running. The alternator is driven by a fan belt or serpentine belt and provides a consistent steady flow of direct current of around 14 or 15 volts. The amount of voltage is kept steady even at varying engine revolutions by a voltage regulator.
How do you measure the voltage on a car alternator?
get a multi meter that reads dc voltage & touch the black (negative -) wire to the negative battery post & the red (positive +) wire to the positive battery post with car running. car off is battery voltage, car on is alternator voltage.
How do you know if the battery is no good on a 2000 ml320?
Should really charge it then test it with a proper battery load tester. All you can do on your own is get a multimeter and check the voltage. Without it running and having sat for a 1/2 hour or so the voltage should be approx 12-12.5 volts. Start the engine and if the alternator is good the voltage at the battery terminals should be 13-14 volts. If without the engine running the battery voltage is 12 or less this may indicate that the battery is not holding a charge. Even then the voltage should go to between 13-14 volts when engine is started showing that the alternator is working to charge the battery. If when started the battery voltage stays around 12-12.5 volts or less I would suspect the alternator. Just to double check there is the main power out terminal on the back of the alternator. With the engine running check the voltage. If 13-14 volts is present at the alternator but not the battery the circuit in between the alternator and battery is suspect. If the voltage at the alternator is the same as at the battery (12-12.5 or less) the alternator or voltage regulator may be defective.
Why wont your brand new alternator recharge your battery?
Maybe the battery is defective. Check the voltage at the battery terminals with the engine running at idle. You should get 13.5 to 16 volts. If not the alternator is defective or the voltage regulator is bad. If you are getting the correct voltage, the battery is bad or the connections are corroded.
What causes the battery to drain when running?
Defective alternator or voltage regulator. Also possibly the battery is defective with a dead cell.
What is alternator?
It is a device that converts mechanical energy to electrical energy on a car. It works by:the alternator creates an electric field by spinning a magnetic rotor with direct current inside stator windings. an ac voltage is developed and rectified dc. this voltage is compared to the battery voltage and determines the current through the rotor. if the battery voltage is lower than the alternator voltage, more current through the rotor increases the magnetic field and creates a larger alternator voltage. if the battery voltage is higher, less current through the rotor decreases the alternator voltage.
