Is your BMW E46 key fob becoming less responsive? Do you have to press the buttons multiple times or get closer and closer to your car for it to work? You might be experiencing a common issue: a dying E46 Key Fob Battery. Many believe the myth that these key fobs recharge while driving, but unfortunately, that’s not true. The reality is, like any battery, the e46 key fob battery eventually needs replacing.
Before you rush to a dealership and spend a significant amount on a new key fob or professional battery replacement, consider this: you can easily replace the e46 key fob battery yourself at home with a few simple tools and a bit of patience. This guide will walk you through the process step-by-step, saving you time and money.
Symptoms of a Failing E46 Key Fob Battery
Recognizing the signs of a weak e46 key fob battery can save you from being stranded or inconvenienced. Here are the common symptoms to watch out for:
- Reduced Range: You need to be much closer to your BMW for the key fob to lock or unlock the doors.
- Intermittent Operation: The buttons become less reliable, requiring multiple presses to activate functions.
- Non-Responsiveness: Eventually, the key fob may stop working altogether, even at close range.
- Security System Issues: Difficulty arming or disarming the car’s alarm system using the remote.
If you’re experiencing any of these issues, it’s highly likely that a fresh e46 key fob battery is the solution.
Tools You’ll Need for E46 Key Fob Battery Replacement
Gather these tools before you begin to ensure a smooth and efficient e46 key fob battery replacement:
- Vice-Grip: To securely hold the key while opening the fob.
- Paint Scraper: A thin, sturdy scraper to start separating the glued fob halves.
- Sharp Knife: For carefully slicing along the seam of the fob to break the adhesive.
- Small Screwdriver or Chisel: To help pry off the old battery leads.
- Soldering Iron (Small Tip Recommended): For desoldering and soldering the battery leads.
- Silver Solder: For creating secure and conductive solder joints.
- Wide Jaw Pliers (Channel-Locks): To hold the circuit board steady during soldering.
- Rubber Band: To apply gentle pressure to the pliers, freeing up your hands.
- New VL2020 Battery with Tabs (or Plain VL2020 Battery): The correct replacement battery for your E46 key fob.
- Plastic Glue: To re-seal the key fob case securely.
- Clamps or Rubber Bands: To hold the fob halves together while the glue dries.
Step-by-Step Guide to Replacing Your E46 Key Fob Battery
Follow these detailed steps to replace your e46 key fob battery successfully:
1. Opening the E46 Key Fob
The E46 key fob is notoriously glued shut, so opening it requires care and patience.
- Secure the Key: Hold the metal key part of the fob firmly in the vice-grip. This provides a stable base for working.
- Start with the Scraper: Insert the paint scraper into the seam at the keyring end of the fob.
- Slice and Pry: Carefully use the sharp knife to slice along the seam where the two halves of the fob case meet. Gently pry upwards with the knife or scraper as you slice to start separating the glued sections. Work your way around the entire perimeter of the fob, taking your time to avoid damaging the plastic case.
Alt text: Close-up showing a paint scraper and knife being used to carefully open the glued seam of a BMW E46 key fob, with the metal key held in a vice-grip for stability.
2. Removing the Old E46 Key Fob Battery
Once the fob is open, you’ll see the circuit board and the battery.
- Identify the Battery: The battery is typically a Panasonic VL2020 with custom leads soldered to it.
- Prepare for Desoldering: Take the wide jaw pliers and grip the circuit board to hold it steady. Secure the pliers with a rubber band around the handles to maintain gentle pressure and free up your hands for soldering. Be careful not to squeeze too tightly, as you could damage the circuit board.
- Desolder the Leads: Using a hot soldering iron with a small tip, carefully apply heat to the points where the battery leads are soldered to the circuit board on the back side of the PCB. Wait for the solder to melt, then gently pull the lead free. Repeat this for both leads (positive and negative).
- Remove the Old Battery: Once both leads are desoldered, the old e46 key fob battery will be free.
- Detach the Leads (If Necessary): If you purchased a replacement battery without pre-attached leads (which is recommended for easier installation), use a small chisel or pocketknife to carefully pry off the custom leads from the old battery.
3. Soldering in the New E46 Key Fob Battery
Now it’s time to install the new e46 key fob battery.
- Solder the Negative Lead: Take the negative lead (the one with the smaller through-pin) and solder it to the bottom (non-writing side) of the new VL2020 battery. Use a small amount of solder to ensure a good connection.
- Resolder Negative Lead to PCB: Position the new battery on the white insulating pad on the circuit board. Resolder the negative lead back into its original position on the PCB. Double-check the orientation to ensure correct polarity.
- Solder the Positive Lead: Solder the positive lead (larger through-pin) to the top (writing side) of the new battery and then resolder it to its corresponding point on the circuit board.
Alt text: Detailed view of the opened E46 key fob circuit board, highlighting the battery compartment, positive and negative lead positions, and the white insulating pad where the new battery will sit.
4. Reassembling the E46 Key Fob
With the new e46 key fob battery installed, it’s time to put the fob back together.
- Clean the Fob Edges: Remove any frayed plastic or old glue from the edges of the fob halves to ensure a clean and tight seal.
- Test Fit: Before applying glue, try mating the fob halves without the circuit board inside to check the fit and ensure they close properly.
- Apply Glue: Apply a thin bead of plastic glue along the perimeter of one half of the fob case.
- Reinsert Circuit Board: Carefully place the circuit board back into one half of the fob case, ensuring it sits correctly.
- Clamp the Fob Halves: Carefully align and press the two halves of the fob together. Use clamps or rubber bands to hold them firmly in place while the glue dries completely, following the glue manufacturer’s recommended drying time.
5. Re-sequencing Your E46 Key Fobs
After replacing the e46 key fob battery, you may need to re-sequence your key fobs to ensure they work correctly with your BMW.
- Prepare Keys: Gather all your E46 key fobs. Choose one key to designate as the “initial” key for sequencing purposes.
- Enter the Car: Get into your BMW, close all doors, and ensure the doors are unlocked.
- Turn Ignition to Position 2: Insert the “initial” key into the ignition and turn it to position 2 (just before starting the engine, when all the dashboard lights illuminate).
- Remove Key and Press Buttons: Remove the key from the ignition. Immediately hold down the unlock button on the key fob. While holding the unlock button, press the lock button three times in quick succession. Release all buttons.
- Check for Response: The car’s central locking system should respond by locking the doors and then unlocking the driver’s door to confirm successful sequencing.
- Repeat for Other Keys: If you have additional key fobs, repeat step 4 for each key within 30 seconds of the previous key sequencing.
Important Note: Any key fobs that are not re-sequenced during this process will not function properly and will need to be included in a repeat sequencing procedure.
Battery Type and Where to Buy
The e46 key fob battery you need is a Panasonic VL2020 3V lithium battery. You can find these batteries online from various retailers. When searching, you can look for:
- VL2020 battery
- Panasonic VL2020 with tabs (if you prefer pre-soldered leads, though plain batteries are often easier to work with for DIY soldering)
- BMW E46 key fob battery replacement
Be aware of shipping restrictions on lithium batteries, and consider purchasing from a local supplier to minimize shipping costs and delivery time.
Conclusion
Replacing your e46 key fob battery is a straightforward DIY task that can save you a trip to the mechanic and the expense of a new key fob. By following these steps carefully, you can restore full functionality to your BMW E46 key fob and enjoy the convenience of remote locking and unlocking once again. With a little patience and the right tools, you’ll be back on the road with a reliably working key fob in no time!
