Is your 2008 BMW 328xi key fob acting up, especially when the temperature drops? Many BMW owners experience issues with their key fobs in cold weather, noticing problems like the car not locking or unlocking remotely, or losing personalized settings like radio presets after starting the engine. If this sounds familiar, the culprit is likely a low battery in your key fob. Fortunately, replacing it is a straightforward DIY task you can accomplish at home, saving you a trip to the dealership and unnecessary expense. This guide will walk you through each step to replace your 2008 BMW 328xi key fob battery efficiently.
Before you begin, you’ll need to gather a few items to ensure a smooth and successful battery replacement.
Tools and Materials You’ll Need:
- Replacement Battery: It’s crucial to get the correct battery. For the 2008 BMW 328xi key fob, you’ll need a VL2020 lithium-ion battery. These are readily available online. Pay close attention to the battery terminal orientation when purchasing, as they need to match your original battery. A suitable replacement can be found online, for example here.
- Sharp X-Acto Knife or Precision Knife: Essential for carefully opening the glued key fob casing.
- Non-Metallic Pry Tool: A credit card or plastic pry tool will help to gently lift the battery without damaging the circuit board.
- Soldering Iron and Solder: For desoldering the old battery and soldering in the new one. If you’re not comfortable soldering, consider seeking assistance or practicing beforehand.
- Optional: New Key Fob Housing: If your current housing is damaged or you want a fresh look, you can purchase a replacement housing.
- Optional: Cyanoacrylate Glue (Gel Type): If you’re reusing the original housing, a small amount of gel-type super glue will be needed to reseal it.
Once you have everything prepared, follow these step-by-step instructions to replace your 2008 BMW 328xi key fob battery.
Step-by-Step 2008 Bmw 328xi Key Fob Battery Replacement:
Step 1: Carefully Open the Key Fob
The BMW key fob is designed to be sealed, so you’ll need to carefully cut it open.
- Take your sharp X-Acto knife or precision knife and gently start cutting along the seam of the key fob. Work slowly and patiently.
- Avoid cutting too deep. The goal is to separate the two halves of the plastic casing without damaging the internal circuit board (PCB). Multiple shallow passes are better than forcing a deep cut.
- Continue around the entire seam until you can gently pry the fob open.
Step 2: Desoldering the Old Battery
With the key fob open, you’ll see the circuit board and the battery.
- Use a non-metallic pry tool, like a credit card, to gently apply a small amount of upward pressure to the battery. This will help when desoldering the terminals.
- Locate the battery terminals. Identify the corner terminal and the terminal closer to the center of the battery.
- Start with the corner terminal. Apply heat from your soldering iron to the solder joint of the corner terminal. Once the solder melts, the terminal should release.
- Repeat for the remaining terminal. The terminal closer to the middle has a longer lead, so it will be easier to remove after the corner terminal is free.
- Remove the old VL2020 battery.
Step 3: Soldering the New Battery
Now it’s time to install the new VL2020 battery.
- Position the new battery into the battery holes on the PCB. Ensure the battery is oriented correctly, matching the polarity of the old battery.
- Hold the PCB by its edges and gently press the battery down into place.
- Apply heat to the middle terminal of the new battery. Melt the existing solder on the PCB to secure the middle terminal.
- Repeat for the corner terminal. Ensure both terminals are securely soldered to the PCB.
Step 4: Test Your Key Fob
Before fully reassembling, it’s crucial to test if the new battery is working.
- Carefully place the PCB back into one half of the key fob housing.
- Test all the key fob functions: lock, unlock, trunk release, and panic button.
- Also, start your 2008 BMW 328xi and check if your personalized settings are now being saved.
If everything works as expected, congratulations! You’ve successfully replaced your BMW 328xi key fob battery. If not, double-check your soldering and battery orientation.
Step 5: Reassemble the Key Fob
Now you can finalize the repair.
- If you have a new key fob housing, carefully transfer the PCB into the new housing and snap it closed.
- If reusing the original housing, apply a small amount of gel-type cyanoacrylate glue sparingly to the edges of the housing. Be careful not to get glue on the PCB or buttons.
- Press the two halves of the key fob housing together firmly and hold until the glue sets.
Your 2008 BMW 328xi key fob should now be working perfectly, even in cold weather. By following these steps, you’ve saved yourself time and money by performing this key fob battery replacement yourself. Enjoy the convenience of a fully functional key fob!
