If it does start, but dies when unhooking the jumper cables, your alternator likely isn't providing the current your vehicle needs to keep running. If it starts and continues running after removing the jumper cables, your battery was likely dead and you may need a new one or to have it charged.
If you hear a whine or the sound goes fuzzy when you hit the gas, your alternator is probably failing. If the vehicle won't crank or start but the headlights are still working, look to problems with the starter or other parts of the engine.
“With the car running, you can turn on all the heavy loads; turn on the heater blower motor, turn the lights on, etc.,” he tells us. “Then check the voltage at the battery terminals. That'll give you a general idea of the health of the alternator.”
Start the engine and turn on dipped beam headlights to run the test. As in the multimeter method, you must first remove the minus terminal from the battery. The alternator works fine if the headlights give a steady light and the engine beat does not go off.
The answer is simple - Yes, You can jump-start a car with a bad alternator. But, can You drive such a car, and for how long, that is another question.
The question is, can a faulty alternator destroy a new car battery? The answer is that a bad alternator, does not always affect the car battery, especially if the battery is new. However, there are chances that the faulty alternator can kill your new battery.
Alternators have a number of moving parts, so as they get dirty and are subjected to extreme temperatures, those internal components can wear out, causing the alternator to go bad. One of the most common problems you're likely to experience with an alternator is a failure in the bearings.
When you have a bad starter motor, there are two ways to crank up your engine: Jump-start your car. Push-start your engine.
In most cases when a starter goes bad, it's completely random with no warning signs or symptoms of mechanical failure.
Signs of a Bad Starter
A clicking sound can be heard when you turn the key. Turning the keys in the ignition won't start the vehicle, but the dash lights come on.
If the battery is completely dead, it won't have enough power to turn over the engine, even with a jump start. In this case, you'll need to replace the battery to get your car running again. Another reason why a car battery won't jump is because there is a problem with the charging system.
If the alternator isn't working as it should, your battery won't have enough charge to start the engine, but that's not the only problem you may experience. A failed alternator may not be able to provide enough power to the spark plugs, which could make the engine stall while you're driving.
How long can a car last on just the battery? If your alternator fails when you're far from home, you can typically drive up to 200 miles on battery power alone. That's assuming your battery is in good shape and fully charged. Of course, it's best to get the alternator repaired or replaced as soon as you can.
In some cases, it can be severe enough to deplete your fully charged battery overnight. Although you can test any circuit for a parasitic draw, this is how it works for a draw on an alternator, and all you need is a digital multimeter.
With a new starter, battery, and alternator (assuming you have not drained the battery attempting to start it), the starter should attempt to crank over the engine. If the starter does not make any noise when the key it turned to crank over the engine, you have an issue with the fuses, or the circuit.
Trouble Starting or Frequent Stalling
As previously mentioned, trouble starting your engine might mean that your alternator is failing to charge the battery. This means that when you turn the key in the ignition, all you'll hear is a clicking sound instead of the purr of your engine.
Some people believe that you can just tap the alternator with a hammer to get it to operate. You should not do this because it will damage the part and you might even damage the surrounding parts to the car, resulting is a large car repair bill.
An alternator has a lot of moving parts that spin when it's working correctly. If one of these parts starts to work ineffectively or breaks off, you may hear some unusual sounds. If you're hearing a grinding sound in your car, this could indicate that the alternator is going bad.
Most alternators will last between 80,000 and 150,000 miles — or about seven years. However, your driving habits and the area where you live could wear it out prematurely.
Use a voltmeter to check your alternator; rev your engine to 2000 RPM, keep the engine running, and test the battery with the voltmeter. If your voltage goes from ~12.2 V to ~13-14.5 V, your alternator is doing well. If your V stays the same or decreases, that's a bad sign.