How to Know if Subaru Forester Battery is Dead: Diagnose, Causes and Jump Start

By Nick Marchenko, PhD

The battery in your Subaru Forester is an essential element that helps ensure its overall performance. Not only does it provide the intense electrical current necessary to start the engine, but it also contributes power to run accessories, computers and sensors on board.

From powering your interior lighting to allowing your Foresters computer systems, such as your infotainment system and backup camera, to function correctly - the battery plays an important role in keeping your car running smoothly.

When a Forester's battery dies, several symptoms become apparent. You may start to notice the engine sputter as it struggles to crank and an overall decrease in power throughout your vehicle. The lights may dim or flicker, and accessories such as the radio and the air conditioning could completely shut off.

Let's take a closer look at the most common causes of a dead battery in Forester, the most prominent symptoms and how to jump-start the vehicle if this happens.

Signs Your Forester Battery Is Dead

Knowing how to diagnose a dead battery in your Forester can save you time and hassle. If any of these signs are present, it's likely that your car's battery has gone bad and needs to be replaced.

1. Subaru Forester Engine fails to start or turn over

Among the most crucial components of a Subaru Forester's starting system is its battery. It supplies energy to the starter motor that gets your engine going. If the charge level in your battery isn't sufficient, then you may experience slow cranking, or worse, it won’t start at all. In this case, replacing your car's battery should be prioritized. Otherwise, you'll get stuck with no transportation whatsoever.

2. Subaru Forester dashboard warning lights illuminate, click and flicker

When a Subaru Forester's battery fails and doesn't have enough charge to power the starter motor, certain signs may indicate a weak battery. Flickering dashboard lights and a clicking noise when attempting to start the engine are both common symptoms of this issue. 

The clicking noise is usually from either the relay in the fuse box or from the starter solenoid itself, caused by low voltage as a result of insufficient power supplied by the battery.

3. Power windows and other electrical components don't work

When the battery of a Subaru Forester dies, all electrical components – from power windows to air conditioning units - will suffer. As the drained battery provides no electricity, any number of complications can arise depending on which component has been affected. 

To prevent further damage and restore your car's functionality; take it to an experienced mechanic for diagnosis and repair immediately.

4. Keyless entry system doesn't function

If your Subaru Forester's battery is experiencing issues, it has the potential to wreak havoc on its keyless entry system and other features — even rendering you unable to start the vehicle. 

To ensure that any issues related to a dead battery are properly assessed and repaired, make sure to bring your car to an experienced mechanic as soon as possible.

5. The Forester clock resets or loses its time setting

If you have a Subaru Forester and find that the clock has reset or lost its time settings, it is likely due to your battery being dead. Without sufficient power from the battery, some electrical components can cease working correctly. To prevent further issues related to a weak battery, take your vehicle in for evaluation and repair by an experienced mechanic as soon as possible.

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What Causes Subaru Forester Battery Issues

Common causes of a dead battery in a Subaru Forester include:

1. Leaving the lights on for an extended period of time.
2. A faulty alternator.
3. An old or worn-out battery.
4. A parasitic drain on the battery.
5. Extreme temperature changes that affect battery performance.

Charging issues can cause dead batteries in Subaru Foresters. This is due to the battery not being charged properly, which can cause it to deteriorate and eventually die out altogether. 

Suppose you're experiencing issues with your car's battery, such as difficulty starting the vehicle or drained power. In that case, it's best to take it to a qualified mechanic for assessment and repair, as charging problems can be complicated and require professional attention.

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How to Test If The Battery in Forester Is Dead

To get an accurate assessment of the battery in a Subaru Forester, use a multimeter to measure volts. When properly charged, the voltage should read at least 12.6 or higher. However, this is only one indicator of your vehicle's battery state and does not provide full insight into its condition.

If your engine is struggling to start, a voltage drop test can be used to determine if the battery has sufficient charge - it will read lower than 10 volts if there isn't enough electricity. This could be caused by an internal breakdown of the battery, extended periods without use or even a malfunctioning alternator.

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How to Jump Start a Subaru Forester with Dead Battery

To jump start a Subaru Forester with a dead battery, you will need another vehicle with a working battery and a set of jump cables. Here are the steps to follow:

1. Park the working vehicle close to the Subaru Forester, making sure the vehicles do not touch.
2. Turn off both vehicles and pop open the hoods.
3. Locate the batteries in both vehicles and remove the plastic covers.
4. Connect the positive (red) cable to the positive terminal of the dead battery and the positive terminal of the working battery.
5. Connect the negative (black) cable to the negative terminal of the working battery and to a metal surface on the dead vehicle's engine (not the battery).
6. Start the working vehicle and let it run for a few minutes.
7. Start the Subaru Forester. If the battery is too dead, it may take a few attempts to start.
8. Once the Forester has started, remove the cables in reverse order: black cable first, then red cable.
9. Drive the Forester around for a while to recharge the battery and make sure the alternator is working.

Note: Always make sure the cables are connected properly and do not touch each other or any other metal surfaces to avoid sparks or short circuits.

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Nick Marchenko, PhD

Industrial Engineer & Automotive Content Specialist

Nick writes in-depth guides on car clubs, engine specs, vehicle ownership, and modifications, combining engineering knowledge with automotive passion.

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