Is your 2008 BMW 328i key fob acting up, especially when the temperature drops? You’re not alone. Many BMW owners experience issues where their key fob becomes unresponsive in cold weather, failing to lock or unlock the doors remotely. Furthermore, you might notice your personalized settings, like radio presets, resetting every time you start your car. The culprit is often a weak or dead battery in your key fob. Fortunately, replacing it is a straightforward DIY task you can accomplish at home. This guide will walk you through replacing the battery in your 2008 BMW 328i key fob, saving you time and money compared to dealership service.
Before you start, gather the necessary tools and a replacement battery. You’ll need a sharp X-acto knife or similar precision cutting tool, a non-metallic pry tool (like a credit card or plastic spudger), a soldering iron, and the correct replacement battery. It’s crucial to identify the right battery type for your BMW key fob, which is the VL2020 Lithium-Ion battery with a 90-degree terminal offset. You can find these batteries online from reputable retailers.
Step-by-Step Battery Replacement Guide
Step 1: Carefully Open the Key Fob
The BMW key fob is sealed with strong glue, requiring patience and a delicate touch to open without damaging the internal circuit board (PCB). Using your sharp X-acto knife, carefully score along the seam of the key fob casing. Work slowly and shallowly, making multiple passes rather than trying to cut through in one go. Avoid cutting too deep to prevent accidental damage to the PCB inside. Focus on separating the glued seam all around the fob.
Step 2: Desoldering 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 upward pressure to the corner of the battery. Then, apply heat to the corner terminal of the battery with your soldering iron. Once the solder melts, the terminal should release. Repeat this process for the other terminal. Starting with the corner terminal is advisable because the middle terminal has a longer lead, making it harder to access and apply tension initially.
Step 3: Soldering in the New Battery
Now it’s time to install the new VL2020 battery. Position the new battery into the battery holes on the PCB, ensuring the polarity is correct (match the orientation of the old battery). Hold the PCB by its edges and gently press down on the battery to ensure it’s seated correctly. Apply heat to the middle terminal first, allowing the solder to flow and secure the battery in place. Then, solder the corner terminal. The battery terminals should push through the existing solder and settle into position.
Step 4: Test and Reassemble the Key Fob
Before permanently sealing the key fob, it’s crucial to test if the new battery is working. Carefully place the PCB back into the key fob housing and test the key fob’s functions: locking, unlocking, and starting your 2008 BMW 328i. If everything works as expected, congratulations! You’ve successfully replaced your key fob battery.
For reassembly, you have a couple of options. You can purchase a new key fob housing for a fresh look. Alternatively, if you’re comfortable with a slightly less perfect finish, you can simply glue the original 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 thin bead of glue along the seam and press the two halves of the key fob together until the glue sets.
Conclusion
Replacing the key fob battery on your 2008 BMW 328i is a manageable DIY project that can resolve common cold weather key fob issues and restore your personalized vehicle settings. By following these steps and taking your time, you can save yourself a trip to the dealership and the associated costs. Enjoy the renewed reliability of your BMW key fob!
