Experiencing issues with your 2007 BMW key fob, especially when the weather turns cold? It’s a common problem: your key fob might fail to lock or unlock your doors remotely, and upon starting your vehicle, you might notice your personalized settings are missing. Before assuming a major malfunction, the solution could be as simple as replacing the key fob battery. This guide will walk you through replacing the battery in your 2007 BMW key fob, a straightforward DIY task that can save you time and money.
Step 1: Procure the Correct Replacement Battery
The first crucial step is to obtain the right battery. For 2007 BMW key fobs, you’ll typically need a VL2020 lithium-ion battery. It’s vital to note the orientation of the terminals on your original battery before purchasing a replacement, as they are usually offset at approximately 90 degrees. You can find suitable batteries from online retailers.
Step 2: Carefully Open the Key Fob Casing
BMW key fobs are notoriously sealed. To access the battery, you’ll need to carefully open the fob. Employ a sharp X-acto knife or a similar precision cutting tool. Patience is key here. Work slowly along the seam of the fob, applying gentle pressure. Avoid cutting too deeply, as the internal circuit board (PCB) is located just beneath the surface, and damaging it will render your key fob useless.
Continue carefully cutting along the seam on the other side of the key fob to fully separate the two halves of the casing.
Step 3: Desolder the Old Battery
Once the fob is open, you’ll see the PCB with the battery soldered in place. To remove it, you’ll need a desoldering tool and a non-metallic prying tool. A credit card or plastic pry tool works well as it minimizes the risk of short-circuiting or damaging the PCB. Gently slide the plastic card under the edge of the battery to apply slight upward tension. Focus on the corner terminal first. Apply heat to the corner solder joint with your desoldering tool until the solder melts and you can lift the terminal free. The terminal closer to the battery’s center has a longer lead, making it easier to remove once the corner is desoldered.
Step 4: Solder in the New Battery
With the old battery removed, position the new VL2020 battery into the battery holes on the PCB. Hold the PCB by its edges and gently press the new battery down into place. Apply heat to the middle terminal solder point first, allowing the solder to reflow and secure the battery terminal. Repeat this process for the corner terminal, ensuring both terminals are firmly soldered to the PCB.
Ensure a secure connection by soldering the top terminal of the new battery to the PCB, completing the circuit for the 2007 BMW key fob.
Step 5: Test the Key Fob
Before permanently reassembling the key fob, it’s crucial to test if the battery replacement was successful. Dry fit the PCB back into the housing and test all key fob functions – locking, unlocking, and remote start if applicable. If everything works as expected, congratulations! You’ve successfully replaced your 2007 BMW key fob battery. If not, double-check your soldering and battery orientation.
Step 6: Reassemble the Key Fob
Finally, you can reassemble the key fob. You have a couple of options here. You could purchase a new replacement housing for a fresh look. Alternatively, if you’re prioritizing practicality, you can simply glue the original housing back together. If opting for glue, use a gel-type cyanoacrylate glue sparingly. Gel glue is less likely to run and minimizes the risk of accidentally gluing the PCB to the housing. Apply a small amount along the seam and carefully press the two halves of the key fob together until the glue sets.
By following these steps, you can effectively replace your 2007 BMW key fob battery and restore its functionality, saving yourself the expense of dealership replacement services. Remember to always test your key fob after reassembly to ensure everything is working correctly.
