Is your 2005 BMW 325i key fob starting to act up? Experiencing issues like needing to press buttons multiple times or having to be right next to your car for it to respond? It’s a common problem, and more often than not, the culprit is a dead or dying key fob battery. Forget the urban legend that your BMW magically recharges the key battery while driving – it’s simply not true. The good news is, replacing the battery in your 2005 BMW 325i key fob is a straightforward DIY task that can save you a trip to the dealership and some cash.
This guide will walk you through the process of replacing your 2005 BMW 325i key fob battery step-by-step. While the key fob is designed to be sealed, with a few basic tools and a little patience, you can easily open it, replace the battery, and get your remote working like new again.
Tools You’ll Need
Before you begin, gather these tools:
- Vice-Grip or Pliers: To firmly hold the key.
- Paint Scraper or Thin Pry Tool: For initial prying.
- Sharp Knife or Precision Blade: To carefully cut along the seam of the fob.
- Small Screwdriver or Chisel: To help separate the battery leads.
- Soldering Iron (Fine Tip Recommended): For desoldering and resoldering.
- Silver Solder: For making secure electrical connections.
- Wide Jaw Pliers (Channel-Locks): To hold the circuit board.
- Rubber Band: To apply gentle pressure to the pliers.
- Plastic Glue: To reseal the key fob.
- Replacement Battery: Panasonic VL2020 with tabs or standard VL2020 battery: Ensure you get the correct battery type.
Step-by-Step Battery Replacement
1. Opening the Key Fob
The 2005 BMW 325i key fob is glued together, so you’ll need to carefully open it.
- Secure the Key: Hold the metal key part of the fob firmly with your vice-grip. This provides leverage and stability.
- Start Prying: Begin at the key ring end of the fob. Insert the paint scraper or thin pry tool into the seam.
- Slice and Pry: Use the sharp knife to carefully slice along the seam where the two halves of the fob meet. Simultaneously, gently pry with the scraper to start separating the case. Work your way around the entire perimeter of the fob, being patient and applying steady pressure.
Alt text: Close-up of a BMW E46 key fob being opened, revealing the internal circuit board and battery compartment.
2. Accessing the Battery
Once the fob is open, you’ll see the internal components.
- Identify the Battery: The battery is located on one side of the printed circuit board (PCB). In the 2005 BMW 325i key fob, it’s a Panasonic VL2020 battery.
- Note the Battery Orientation: Observe how the battery is positioned and the connection of the positive (+) and negative (-) leads to the PCB. The negative lead is typically on the upper left, and the positive lead on the upper right. These leads are also keyed with different pin sizes on the PCB.
Alt text: Detailed view of the BMW E46 key fob circuit board highlighting the battery well and lead connection points.
3. Removing the Old Battery
- Secure the PCB: Grip the PCB with the wide jaw pliers and use a rubber band around the handles to maintain gentle pressure. Be careful not to squeeze too tightly, as you could damage the circuit board.
- Desolder the Leads: Apply the hot soldering iron to the back of each battery lead on the PCB. Wait for the solder to melt, then gently pull the lead free. Repeat for both leads to remove the old battery.
- Remove Battery Leads (If Necessary): If you purchased a standard VL2020 battery without pre-attached leads, you’ll need to carefully remove the custom leads from the old battery using a small chisel or knife. These leads will be reused on the new battery, if needed. However, using a replacement battery with pre-attached leads simplifies this step. If using a plain battery, solder the old leads to the new battery, ensuring correct polarity. Solder the negative lead to the flat side of the battery (usually without writing) and the positive lead to the opposite side. Use minimal solder to maintain a tight fit within the fob.
4. Installing the New Battery
- Solder the Negative Lead: Solder the negative lead of your new battery to the corresponding point on the PCB. Ensure it’s securely attached. The negative lead pin is smaller than the positive one – double-check orientation.
- Position the Battery: Once the negative lead is soldered, the battery should sit correctly within the white insulating pad on the PCB.
- Solder the Positive Lead: Solder the positive lead to its designated point on the PCB. The order doesn’t matter if the negative side is correctly connected first.
5. Reassembling the Key Fob
- Clean the Fob Edges: Remove any frayed plastic edges from the fob halves to ensure a clean closure.
- Test Fit: Before applying glue, try mating the fob halves together without the PCB inside to check the fit. Then, reinsert the PCB and check the fit again.
- Apply Glue and Clamp: Apply a thin, even bead of plastic glue around the perimeter of one fob half. Carefully align and press the two halves together. Use clamps or rubber bands to hold the fob firmly closed while the glue dries, following the glue manufacturer’s instructions for drying time.
Re-sequencing Your BMW 325i Key Fob
After replacing the battery, you’ll need to re-sequence your key fobs to your 2005 BMW 325i.
- Prepare Your Keys: Gather all your BMW 325i key fobs.
- Enter the Car: Get inside your BMW, close all doors, and ensure the doors are unlocked.
- Initiate Sequencing with First Key: Insert the first key into the ignition and turn it to position 2 (ignition ON, all dash lights illuminated, but engine not started).
- Remove Key and Button Press: Remove the key from the ignition. Immediately press and hold the unlock button on the key fob. While holding the unlock button, press the lock button three times in quick succession. Release all buttons. The car’s central locking system should respond by locking and then unlocking the driver’s door, indicating successful sequencing of this key.
- Repeat for Remaining Keys: For each additional key fob, repeat the button press sequence (hold unlock, press lock three times, release all).
Important Note: Any key fob not re-sequenced during this procedure will not function correctly. You’ll need to repeat the entire re-sequencing process to include any missed keys.
Now you should be able to drive off with a fully functional key fob. You’ve successfully completed your 2005 Bmw 325i Key Fob Battery Replacement!
