What is draining my car battery when its off?

What may drain a car battery when it's off are things such as interior lights, door lights, or even bad relays. While your engine runs, the alternator recharges the battery — which is why you typically don't have to worry about the battery dying while you're blasting the radio on your drive to work!

Why is my car battery draining when not in use?

There may be a problem in the starting system. A short circuit may cause excessive current draw and drain your battery. Check the charging system for a loose or worn-out alternator belt, problems in the circuit (loose, disconnected or broken wires), or a failing alternator.

Can a blown fuse drain a car battery?

No a burnt fuse can't cause battery drain issues. Some fuses don't get power until the circuit is turned on so don't be concerned about them. Has your battery been replaced or load tested to make sure it's good?

How do you trace a parasitic drain?

Can a alternator drain your battery?

Contrary to its purpose, an alternator can drain a battery. It's rare, but it's possible. A draw on the battery only occurs if there's a problem with either a component in the alternator itself or connections to it.

How to Test and Find a Parasitic Battery Drain (Key Off)

How do you check for a parasitic draw on a car battery?

Pull the negative off the battery. Put the test light between the post and the ground wire. If the light illuminates, you have a draw. Use the fuse pull method to find the draw; when the light goes out, you found the draw.

Can a bad alternator drain your battery when the car is not running?

A corroded or defective alternator diode will faultily continue charging the circuit even when the car off. This, in turn, will drain your car battery and cause the car not to start.

How can I tell if my alternator is bad?

What happens if alternator fuse is bad?

If the alternator's fuse or fusible link is blown, the alternator will not be able to charge the battery. The battery then doesn't store enough power for starting the car or keeping it running.

Which battery terminal Do I disconnect to check 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 do you check alternator for parasitic draw?

With the engine running, touch the meter probes to the battery terminals—positive (red) meter probe to the battery positive terminal, and negative (black) meter probe to the battery negative terminal. If you find more than 0.5 ACV, it's likely the alternator's rectifier has one or more bad diodes.

Can AutoZone test the alternator?

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

What is considered a parasitic draw?

Parasitic draw, also called drain, is the electric current that flows through a vehicle, both while it runs and after the ignition is turned off. You know how you can forget to turn off your headlights, and then your car won't start the next day? Well, this is just one example of parasitic drain.

How much does it cost to do a parasitic draw test?

The average cost for battery test is between $35 and $44.

What can cause parasitic battery drain?