Why Car Radio Won’t Turn on After Replacing Battery?

At some point, your car battery dies or malfunctions, so you change it, however, after the replacement, your car radio often refuses to switch on.

But why the radio does not turn on after replacing the battery? Let’s find out.

In general, your car radio won’t turn on after replacing the battery because of a damaged fuse, a locked radio, or an improperly installed battery. Fuse or radio damage happens when electrical surges are too high, while a car’s security feature results in a locked radio after battery replacement.

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Tip: Before replacing any car battery, it is worth plugging a memory saver into your car’s cigarette or accessory outlet. You can also buy a memory saver with a built-in battery.

APSG Battery Saver and VSTM OBD II are my favorite and inexpensive options if you are on a budget.

However, if you prefer a complete kit that will not only save memory but will also protect and help with charging the battery, try Li Lead Battery Protector, Ezred Memory Saver on Amazon.com.

In this article, I will show you the possible causes of radio malfunction after battery replacement and their quick fixes. Similarly, you’ll gain a better understanding of why these issues happen and other related things.

Radio Malfunction After Battery Replacement

When you replace your battery, two things happen:

  • First, you’re disconnecting your car’s electrically-powered components from their power source.
  • Second, you’re exposing the components mentioned above to a possibly high electric surge when you turn on your car after replacing its battery.

Improper handling and procedures could result in damages to your car from this alone. The sudden electric surge can blow your radio’s fuses or cause internal damage within it. However, that is not where it ends. 

car radio wont turn on after replacing battery

During the whole battery-changing process, you or the person replacing your battery may miss some crucial steps or neglect essential things by accident. For example, you may not know that you need a memory saver during battery replacement to ensure your car’s radio and everything else does not reset. 

When this happens, you will end up with a car suffering from memory loss once you turn it back on. Likewise, you may lose access to your radio, where it will ask you to input an anti-theft code or where you are unable to set its time right.

What Happens When You Disconnect Your Car’s Battery?

The average person wouldn’t usually think about what happens when they disconnect their car’s battery. Since you can power everything on and off without much thought or consequence, you may think the same goes for your car.

However, remember that even phones and computers need to follow proper shutdown procedures to ensure you’ll receive no data loss. Similarly, other electronic devices need their controls switched off to ensure that no damage occurs to them. 

Hence, when you’re disconnecting your car battery, you need to follow proper procedures or risk having the following issues on your car:

Memory Loss Occurs When You Disconnect a Modern Car’s Battery

You may not know about this if you’re only familiar with replacing older car models, but modern cars need a memory saver when you’re disconnecting their batteries.

If you neglect using a memory saver, your car is bound to lose most of its memory within 5 to 10 minutes of battery disconnection. This is because your car’s computer needs constant power to remember your preferences and stored settings.

So, once you finally turn on your car after replacing its battery, you’ll notice your car runs differently and displays different settings. Similarly, your car may even ask you to input a code before you can access and use its computer.

Your Car’s Radio May Ask for a Code After a Battery Replacement

This is a part of a modern car’s security feature: asking for a code before using your radio after you replaced its battery. If somebody steals your car, the code prevents the thief from using your car’s radio, among other things.

You May Experience Starting Problems and Driveability Issues

You spent plenty of time with your car, driving it around and allowing it to know your preferences, and it stored all the information it learned from you into its computer.

However, when you disconnect its battery for a long period, its memory resets, so it forgets your preferred settings. As a result, you may experience driveability issues like a poor-running engine, malfunctioning sensors, weird transmission functions, and other things. You may have issues starting your car, too. 

Your Air Conditioning, Car Radio, and Power Accessories May Enter a Constant State of Malfunction

Your air conditioners act up due to the resetting of your car’s climate control module. 

Meanwhile, your car reset radio isn’t turning on due to memory loss, and your power accessories aren’t working properly because your body control module also reset itself.

Of course, you’re learning these a little too late. Your car may showcase one or two of these issues already, especially the radio malfunction part. However, know that they’re not permanent damages. They’re fixable, but some of them may cost quite a lot.

If you want to watch an entertaining clip that explains why battery disconnection harms your car, check out a short video from Scotty Kilmer:

What Happens When You Turn On Your Car After Replacing Its Battery?

You wouldn’t damage your car’s components if you installed the new battery correctly. However, if you mishandle a part of the installation process, you risk fuse issues and such.

Now that you have a better understanding of what happens when you disconnect and reconnect your car battery, you’ll easily discern why your car radio isn’t turning on after you replaced your battery. I will explain the top three reasons below and suggest ways to fix them.

Your Car Suffered Fuse Damage

Fuses are short wires with specific compositions and diameters, and they exist to prevent fires, electrical shocks, and other things from happening. When you start your car after you replace its battery, you may blow up a fuse within your radio’s system. That fuse will prevent your car radio from working.

To diagnose if your car radio suffers from a blown or damaged fuse, you’ll need to:

  1. Disconnect your car battery.
  2. Open your car’s fuse compartment that’s usually located behind the radio.
  3. Check each fuse for signs of damage.
  4. Blown fuses often look fried or melted.

Once you determine that your car radio isn’t working after battery replacement because of a blown fuse, you can fix this by replacing your fuse.

To replace your car radio’s fuse:

  1. Consult your car’s owner manual for fuse specifications.
  2. Buy or obtain the specified fuse.
  3. Remove the damaged fuse and place the new fuse in the compartment.

Your Car’s Security Feature Locked Your Radio

Your car radio may refuse to turn on if the battery replacement activated your radio’s anti-theft feature. Modern car manufacturers placed this security feature to prevent thieves from accessing your car’s computer module, but you may find it bothersome when all you did was replace your battery.

You’ll know your car radio is locked when it shows LOCKED on its screen or simply asks you for a code. You can find your car radio’s code in four ways:

  1. Read through your owner’s manual to check for the code.
  2. Check your car manufacturer’s website for a self-service section that allows you to figure out your radio code by entering your car’s vehicle identification number, year, make, and model.
  3. Reach out to your car manufacturer’s customer service representatives for assistance.
  4. Contact your local dealership for help.

Your Battery Installation Method Damaged Your Car Radio

As mentioned earlier, you need to replace your car’s battery by following proper procedures and taking necessary precautions. If you skip those, it results in car component damage, including radio damage.

You may try the steps we’ll mention below in an attempt to fix your car radio. However, if those steps don’t work, it may mean that your radio suffered internal damage. Bring it to your local dealership to have it checked.

If your car radio suffered internal damage, your best option is to replace it. 

What to Do When Your Car Radio Won’t Turn On

Besides the quick fixes mentioned above, here are some other things you can do when your car radio won’t turn on after you replaced its battery:

  • Disconnect and reconnect the pigtail connector or replace it. Sometimes, all it takes to fix a car radio that refuses to turn on after a battery replacement is the disconnection and reconnection of its pigtail connector. Hence, try disconnecting your connector for about 15 minutes before reconnecting it again, and then turn on your radio.
  • Observe your head unit for power. If you find no fault or damages on your connections and fuses, check your power wires. Your car has two: one is constantly hot, and the other only heats up when you turn on your ignition. Having these wires on reverse results in a radio that won’t turn on, and having them on low or without power means they are broken, resulting in a faulty radio. Replace your power wires if this is the case.
  • Check your head unit for ground. You’ll notice ground loops instead of total failures if your car has ground issues, but it’s still wise to check on it when your radio won’t turn on. To do this, use a multimeter on the head unit pigtail and ground on your car’s body. A poor ground result means the ground itself isn’t the only reason for your radio failure, while a disconnected ground means the ground is at fault.
  • Test your head unit. If you can’t think of anything else to test and check, connect your ground and power leads to a 12V negative and positive. Replace your head unit or leave it alone, depending on the result.
  • Look for your car’s owner manual and see if there’s a solution there. Most cars possess complete troubleshooting guides, so there’s a chance you’ll find a solution here.
  • Turn the ignition key just enough to start your car’s basic functions but not the engine, and then let it sit for 10 minutes. This is useful if your car forgot your radio’s vehicle identification number and locked you out.
  • Turn off every power component in your car, including your speaker volume and air conditioners, and then disconnect and reconnect the battery. Leave the battery disconnected overnight for best results.
  • View your car’s body control module and assess if any fault codes exist there. Of course, older car models may not suit this method, so skip this if that’s the case.
  • Visit your local dealer and ask them to use their factory scanner to revive your radio. In some cases, the factory scan tool solves the car radio problem. However, note that this may take a few hours.
  • Replace your car radio. It’s expensive to replace your car radio, but it may be the only way if your car radio won’t turn on after battery replacement. This is especially true if your car radio suffered internal damage.

How to Replace Your Car Battery the Right Way

Of course, you learned your lesson when you couldn’t turn on your car radio after replacing its battery. So, you want to learn the correct way of replacing your battery for future reference. Here’s how:

Buy a Memory Saver

A memory saver is crucial to ensure your car’s data remains the same. It charges your car radio and other electric-dependent car components while your battery is disconnected. This prevents memory loss from happening and saves you from future headaches like a malfunctioning car radio.

You can plug your memory saver into your car’s cigarette or accessory outlet, or you can buy a memory saver with a built-in battery. APSG Battery Saver and VSTM OBD II are inexpensive options if you are on a budget. However, if you prefer a complete kit that will not only save memory but will also protect and help with charging the battery, check out Li Lead Battery Protector or Ezred Memory Saver on Amazon.com now.

Don’t forget to arm yourself with goggles and gloves as well.

Connect Your Memory Saver and Plug It Into Your Car’s Accessory Outlet

Of course, you don’t need to plug your memory saver into your car’s outlet if it already features its battery. However, double-check that the memory saver’s battery contains power and ensure that it’s working after you plug it in.

If you’re using a memory saver plugged into your car’s accessory outlet, you may need to turn your ignition on to make it work.

Switch Off All the Other Accessories Within Your Car

You’re using the memory saver to save your car’s most important data, so all you need to connect is your car’s computer part. Hence, switch off your car’s lights, air conditioner, and other battery-powered accessories. This ensures that your memory saver will work as long as possible.

Disconnect Your Car’s Battery

Your exact process of removing your car’s battery will vary on your car’s make and model. However, most cars possess guards and a plastic cover. Sometimes, they may even feature a mounting bracket. Remove these parts with the appropriate tools and proceed with the next steps.

Once you remove the car’s casing, your next step is to disconnect the negative terminal. The negative terminal’s cable must go first. If you remove the positive terminal before removing the negative end, you’ll most likely cause a short within your car’s system. This is because your metal tool may touch another metal in your car when removing the positive end first.

You can figure out which cable houses the negative terminal by looking for the terminals’ minus sign. Similarly, it’ll always be housed under a black cover.

Grab a socket wrench to remove the nut holding the cable’s clamp. Then, remove the cable and place it in a secure place. Ensure that the cable isn’t anywhere near the battery. You can wrap a rag around the terminal for better results so the cable doesn’t hit it.

Next, remove the positive terminal. Its cable is next to the negative terminal, and it’s red. Similar to the negative terminal, ensure that the cable doesn’t touch the battery.

Place the New Battery As Fast as You Can

You can take your time if your memory saver possesses a large battery, but it’s best to be swift when installing a new battery. This reduces the chances of future issues after the installation.

When placing a new battery on your car, reconnect the positive cable first and then the negative cable. Then, double-check if their attachment is secure. Once that’s done, replace the covers, guards, or brackets with new ones.

Finally, switch on your car’s ignition and start your engine. You can now remove the memory saver, and your car’s system should be alright.

You can also view Scotty Kilmer’s YouTube clip for a fast tutorial on disconnecting and reconnecting your car’s battery the right way:

Final Thoughts

Your car radio may not turn on after you replace its battery if you have a damaged fuse, a locked radio, or an improperly installed battery. Damaged fuses are common in car radios, while radio damage occurs from improper installation or electrical surges. Meanwhile, a locked radio happens when your car’s memory resets itself.

Sometimes, you can fix your car radio issue with ease. However, you may need to take more complex steps to turn on your radio if the damage is a bit more complicated than usual. 


Welcome to ImproveCarAudio! I am Martin, and I love to write about everything related to car sound systems. I strive to provide the most accurate and helpful information about car audio through extensive research, as well as my experience with car audio installations.

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