Is your 2007 BMW 3 Series key fob acting up, especially when the weather gets cold? You might be facing a common issue: a dying key fob battery. Symptoms like reduced range or the car not recognizing your personalized settings can point to a low battery. Fortunately, replacing the battery in your BMW E90 key fob is a straightforward DIY task. This guide will walk you through the process step-by-step.
First, you’ll need to purchase the correct replacement battery. The 2007 BMW 3 Series key fob (and many other BMW models) uses a VL2020 lithium-ion battery. It’s crucial to get the right battery type and note the orientation of the terminals before you order. You can find these batteries online from retailers like eBay or specialized battery stores.
Once you have your new battery, the next step is to carefully open your key fob. The BMW key fob is sealed with glue, so you’ll need a sharp X-acto knife or similar precision cutting tool. Gently score along the seam of the fob shell. Take your time and avoid cutting too deep to prevent damage to the internal circuit board (PCB). Patience is key here.
With the fob open, you’ll see the battery on the PCB. Now, you need to desolder the old battery. Using a non-metallic pry tool, like a credit card or plastic spudger, gently apply a little pressure to the battery to create space for desoldering. Start by desoldering the corner terminal of the battery. This is usually easier to access first. A soldering iron and desoldering braid or pump will be needed for this step.
After removing the old battery, it’s time to install the new one. Place the new VL2020 battery into the battery holes on the PCB, ensuring correct polarity. Hold the PCB by its edges and gently press the battery down into place. Apply heat with your soldering iron to the battery terminals on the PCB. Start with the middle terminal, then the corner terminal, allowing the new battery’s terminals to sink into the existing solder.
Before sealing everything up, test the key fob. Insert the PCB into the housing and check if the lock/unlock buttons and car starting function work. If everything is working correctly, congratulations! You’ve successfully replaced your BMW key fob battery.
Finally, 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 original housing back together. If you choose to glue it, use a gel-type cyanoacrylate glue sparingly to avoid it running and potentially damaging the PCB. Apply a small amount along the seam and press the housing pieces together until the glue sets.
Replacing your 2007 BMW 3 Series key fob battery is a cost-effective way to restore full functionality to your key. By following these steps, you can avoid a trip to the dealer and get your key fob working like new again.
