Is your 2012 BMW 328i key fob acting up, especially when the weather gets cold? You’re not alone. Many BMW owners experience issues with their key fobs in colder temperatures, often resulting in a key fob that won’t lock or unlock the doors, or a car that starts without recognizing your personalized settings. The culprit is often a weak or dead key fob battery.
Fortunately, replacing the battery in your BMW 328i key fob is a straightforward DIY task that can save you a trip to the dealership and the associated costs. This guide will walk you through the process step-by-step, allowing you to restore your key fob to its optimal functionality.
Before you begin, ensure you have the correct replacement battery. The 2012 BMW 328i key fob typically uses a VL2020 lithium-ion rechargeable battery. You can find these batteries online from various retailers. Make sure to note the orientation of the battery terminals before you remove the old one, as the new battery will need to be installed in the same way.
Tools and Parts You’ll Need:
- New VL2020 battery for BMW key fob
- Sharp X-Acto knife or similar precision knife
- Non-metallic pry tool (a credit card or plastic spudger works well)
- Soldering iron and solder
- Safety glasses
Step-by-Step Battery Replacement Guide:
Step 1: Carefully Open the Key Fob
The BMW key fob is sealed with glue and doesn’t have screws. To access the battery, you’ll need to carefully cut along the seam of the fob to open it.
Using a sharp X-Acto knife, gently score along the seam line of the key fob. It’s crucial to take your time and avoid cutting too deep, as you could damage the internal circuit board (PCB). Work your way around the entire perimeter of the fob, gradually deepening the cut until you can pry it open. Patience is key here.
Step 2: Desolder the Old Battery
Once the fob is open, you’ll see the PCB with the battery soldered in place. To remove the old battery, you’ll need to desolder it.
Using a non-metallic pry tool like a credit card, gently apply a small amount of pressure under the corner of the battery to create slight tension. Then, apply heat from your soldering iron to the corner terminal of the battery. Once the solder melts, the terminal should release. Repeat this process for the other terminal. It’s generally easier to start with the corner terminal as the center terminal has a longer lead and is harder to access initially.
Step 3: Solder in the New Battery
With the old battery removed, it’s time to install the new VL2020 battery.
Place the new battery into the battery holes on the PCB, ensuring the terminals are aligned correctly (refer to the orientation of the old battery). Hold the PCB by the edges and gently press down on the new battery to ensure the terminals are firmly seated in the holes. Apply heat to the middle terminal first, then the corner terminal, allowing the solder to flow and secure the new battery in place. Ensure a good solder joint for a reliable connection.
Step 4: Test and Reassemble Your Key Fob
Before permanently sealing the key fob, it’s crucial to test if the new battery is working correctly.
Dry fit the PCB back into the key fob housing and test all the key fob functions – locking, unlocking, and starting your 2012 BMW 328i. If everything works as expected, congratulations! You’ve successfully replaced your key fob battery.
Now you can reassemble the key fob. You have a couple of options here. You can purchase a new key fob housing for a fresh look, or simply glue the old housing back together. If you choose to glue it, use a gel-type cyanoacrylate glue sparingly to avoid it running and potentially gluing the PCB to the housing. Apply a small amount of glue to the seam and press the two halves of the fob together until the glue sets.
Conclusion:
Replacing the key fob battery in your 2012 BMW 328i is a cost-effective and satisfying DIY repair. By following these steps, you can restore your key fob’s functionality and avoid the expense of dealership service. This simple maintenance can resolve common key fob issues, especially those exacerbated by cold weather, ensuring your BMW remains convenient and responsive. Remember to always double-check the battery type and polarity before installation to guarantee a successful repair.
