Can you test an alternator by disconnecting the battery?

If you're tempted to test an alternator by disconnecting the negative battery cable, don't do it. A good alternator may indeed keep the engine running without the negative cable, but this was never a good test. In the pre-computer days, you could pull it off without damaging anything.

Do I disconnect the positive or negative to check the alternator?

You can check the alternator by simply starting your car and then disconnecting the negative battery cable. Be careful doing this, though, because there are a lot of moving parts in your engine compartment that could cause injury.

How can I tell if my alternator is bad without a multimeter?

How do I know if it's the battery or the alternator?

An illuminated dashboard light can indicate a problem with an automobile charging system. However, a very simple way to check if the alternator is working is to run the car and disconnect the positive terminal of the battery. If the vehicle stops running, then you probably have a bad alternator.

What battery cable do I remove to test alternator?

Testing the Alternator by Disconnecting the Battery

Can you test an alternator at AutoZone?

Every AutoZone in the USA will check your alternator, starter, or battery at no charge.

Can you unplug alternator while car is running?

HOWEVER, be aware that this test is not without risk to damaged car electronics. If your alternator is malfunctioning by over-charging your battery, disconnecting it may allow the alternator to provide an even higher voltage to the car electronics, and potentially damage those sensitive components.

What happens if you disconnect the battery while the car is still running?

Removing the battery from the circuit allows those spikes and transients to travel around, endangering every semiconductor circuit in your car. The ECU, the speed sensitive steering, the memory seat adjustments, the cruise control, and even the car's stereo.

Can I just disconnect negative terminal?

Q: Can you just disconnect the negative terminal? You can disconnect the battery's negative cable. All you are required to do is to locate the negative polarity of the battery and disconnect the terminal. Avoid the negative terminal to make contact with the positive one.

What happens if you remove the positive terminal first?

It's important to disconnect the negative side of the battery first, otherwise you can cause an electrical short if the positive is removed first.

Will disconnecting battery reset ECU?

A. It depends on the car's age and type of ECU used. On some older cars, disconnecting the battery will reset the system but in most new cars it does nothing, except potentially reset the clock and radio station presets.

Can Oreillys check your alternator?

Your local O'Reilly will test your alternator for free on or off your vehicle so you can know for sure whether or not that's the problem with your vehicle.

What can damage an alternator?

Driving a vehicle through water that is deep enough to splash or flood the alternator can damage the alternator shaft bearings and possibly the brushes and electronics inside the unit as well. Water can also cause corrosion that over time will damage the wiring and bearings inside the alternator.

Can you test an alternator that's not in a car?

A battery test is easy to perform and can be done at home. First, open the hood and start the car. While the engine is running, remove the negative cable from the battery. If the vehicle stalls or dies, the alternator is likely bad.

What tells the alternator to charge?

A VOLTAGE REGULATOR regulates the charging voltage that the alternator produces, keeping it between 13.5 and 14.5 volts to protect the electrical components throughout the vehicle. There is also a system to warn the driver if something is not right with the charging system.