Common Reasons Your Key Fob Isn’t Working After a Battery Change

You’ve just replaced the battery in your car’s key fob, expecting it to work like new—but nothing happens. The doors won’t unlock, the buttons don’t respond, and frustration quickly sets in. While a dead battery is the most common culprit behind a non-functioning key fob, sometimes the issue continues even after a fresh battery is installed. As automotive locksmiths, we see this problem often, often with frustrated customers coming into the shop looking for answers. Here are the most common reasons your key fob might not be working after a battery change.

The Battery Was Installed Incorrectly

It might sound simple, but it’s easy to place the new battery the wrong way around. Key fobs require the positive and negative sides to be aligned exactly as designed. If the battery is flipped or not sitting securely in place, the fob won’t get power. It is a good idea to double-check the polarity markings inside the fob and make sure the battery is firmly seated.

The Battery Contacts Are Dirty or Bent

Over time, the small metal contacts inside your fob can collect dirt or get slightly bent out of shape. Even with a brand-new battery, poor contact means the fob won’t power up. When changing the battery, clean the contacts carefully with a cotton swab and rubbing alcohol. If they look bent, gently adjust them back into place.

The Key Fob Needs to Be Reprogrammed

Some vehicles, and in particular some newer cars, require the fob to be re-synced with the car after a battery replacement. If your fob was already a little glitchy before the battery died, the programming may have reset. A common sign is that the fob has power (lights up or shows activity), but the car doesn’t respond. Depending on your make and model, you may need a locksmith like Mr Car Keys to reprogram the fob. We have a wide range of specialist tools to do the job quickly and effectively the first time.

The Wrong Battery Was Used

Not all key fob batteries are the same. While most use coin-cell batteries like CR2025 or CR2032, using the wrong size or type can cause issues. Even if it fits, the voltage or thickness might be slightly off. Always check your owner’s manual or look at the old battery’s exact code before buying a replacement. If in doubt, call us at Mr Car Keys on 0404621621 for advice and our friendly staff can help you.

Internal Damage to the Fob

If the fob has been dropped, exposed to water, or simply worn out from years of use, internal damage could be to blame. Changing the battery won’t fix broken circuit boards or failed microchips. In this case, you’ll need a professional locksmith to repair or replace the fob.

The Car Itself Has an Issue

Sometimes, the problem isn’t with the key fob at all. Faulty receivers, blown fuses, or electrical issues in the car can prevent the signal from reaching the vehicle. If you have a spare key fob and it doesn’t work either, the issue is likely with the car, not the fob. Again, we have the specialist tolls to be able to diagnose issues like electrical issues or repair or replace things like ignition antennas.

When to Call a Professional Locksmith

If you’ve checked the battery, contacts, and tried basic troubleshooting but your fob still isn’t working, it’s time to call a professional automotive locksmith like Mr Car Keys. We can:

• Test your key fob for proper signal output
• Reprogram the fob to your vehicle
• Replace damaged circuit boards
• Provide you with a new or spare key fob on the spot

 

A non-working key fob after a battery change can be frustrating, but the fix is often simple. By checking the battery orientation, contacts, and compatibility, you can solve many issues yourself. For more complex problems, an experienced automotive locksmith can quickly get you back on the road. So call us on 0404621621 or do an online enquiry at www.mrcarkeys.com.au and let us help you.