Experiencing issues with your 2007 BMW key fob, especially in cold weather? You’re not alone. Many BMW owners find that their key fobs become less responsive, or even fail completely, when temperatures drop. Symptoms can include difficulty locking or unlocking your doors remotely, and even losing your personalized car settings like radio presets after starting the engine. This often points to a simple culprit: a dead or dying key fob battery. Instead of heading straight to the dealership and paying a premium for a replacement, you can easily tackle this yourself. This guide provides a step-by-step walkthrough for replacing the battery in your 2007 BMW key fob, saving you time and money.
Tools and Parts You Will Need
Before you begin, gather these essential items:
- Replacement Battery: You’ll need a VL2020 lithium-ion battery. It’s crucial to get the correct type to ensure proper function and fit. You can find these online from retailers like eBay or Amazon by searching for “VL2020 battery BMW key fob”. Pay close attention to the battery terminal placement when ordering to match your original battery.
- Sharp X-Acto Knife or Precision Knife: For carefully opening the glued key fob casing.
- Small Non-Metallic Pry Tool: A credit card or plastic spudger works well for gently prying and applying tension without damaging electronic components.
- Soldering Iron and Solder: Essential for desoldering the old battery and soldering in the new one. If you’re new to soldering, practice on scrap electronics first.
- Cyanoacrylate Glue (Gel Type Recommended): To re-seal the key fob casing after the battery replacement. Gel type is less messy and prevents run-off.
Step-by-Step Battery Replacement Guide
Step 1: Obtain the Correct Replacement Battery
The first crucial step is to purchase the correct VL2020 battery. These batteries are specifically designed for BMW key fobs and feature solder terminals for PCB (Printed Circuit Board) mounting. Ensure you note the terminal orientation of your current battery before ordering the replacement to guarantee compatibility. Online marketplaces like eBay and Amazon offer these batteries; search for “VL2020 battery BMW key fob” to find suitable options.
Step 2: Carefully Open the Key Fob Casing
The BMW key fob is designed to be sealed, meaning you’ll need to carefully cut it open. Use a sharp X-Acto knife and gently score along the seam line of the fob casing. Multiple shallow passes are better than trying to cut through in one go. Important: Do not cut too deeply as you risk damaging the internal PCB and components. Work slowly and patiently, going around the entire perimeter of the key fob until you can gently pry the two halves apart.
Step 3: Desolder the Old Battery
Once the key fob is open, you’ll see the PCB with the battery soldered in place. To remove it, you’ll need to desolder the terminals. Using a non-metallic pry tool like a credit card, gently apply a small amount of upward tension to the battery. Focus on the corner terminal first. Apply heat from your soldering iron to the solder joint of the corner terminal. Once the solder melts, the terminal should release. Repeat this for the other terminal. Starting with the corner terminal is advised because the middle terminal often has a longer lead, making it harder to apply tension initially.
Step 4: Solder in the New Battery
Place the new VL2020 battery into the designated holes on the PCB. Hold the PCB by its edges and gently press the battery down to ensure the terminals protrude through the solder points. Apply heat from your soldering iron to the middle terminal first, then the corner terminal. The heat will melt the existing solder, allowing the battery terminals to sink into place and create a secure connection. Ensure the battery sits flush against the PCB.
Step 5: Test and Reassemble the 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 functions: locking, unlocking, and starting your BMW. If everything works as expected, congratulations! You’ve successfully replaced your BMW key fob battery.
Step 6: Re-seal the Key Fob
You have a couple of options for reassembling the key fob. For a perfect finish, you can purchase a new replacement housing. Alternatively, you can simply glue the original housing back together. If you choose to glue it, use a gel-type cyanoacrylate glue sparingly. Apply a thin bead of glue along the seam of the housing and carefully press the two halves together. Gel glue is recommended as it prevents running and minimizes the risk of accidentally gluing the PCB to the housing.
Conclusion
Replacing the battery in your 2007 BMW key fob is a straightforward DIY task that can save you a significant amount compared to dealership service costs. By following these steps and taking your time, you can restore your key fob’s functionality and avoid the frustration of a dead battery, especially in cold weather conditions. This simple repair ensures you maintain convenient access to your vehicle and retain your personalized settings every time you drive.
