Accidentally running your Mercedes key fob through the washing machine can be a heart-stopping moment for any car owner. Discovering your key fob soaked after a wash cycle is more common than you might think! If you’ve found yourself in this situation, or perhaps you simply need to replace the battery in your Mercedes key fob, knowing how to safely open it is the first crucial step. This guide will walk you through the process of opening your Mercedes key fob, drawing from real-world experience to help you address issues like water damage or battery replacement with confidence.
Before you panic about a potentially expensive replacement, take a deep breath. Often, a water-damaged key fob can be salvaged with a little careful DIY effort. Even if you haven’t washed your keys, understanding how to open your Mercedes key fob is useful for routine maintenance like battery changes. This guide provides a detailed, step-by-step approach to safely access the internal components of your key fob.
Tools You’ll Need to Open Your Mercedes Key Fob
Before you begin, gather these readily available tools. Having everything at hand will make the process smoother and prevent any further accidental damage to your key fob.
- Isopropyl Alcohol (50-70%): This is essential for cleaning any corrosion, especially if your key fob has been exposed to water. You can find this at any pharmacy or supermarket.
- Q-tips: For precise application of isopropyl alcohol and gentle cleaning of delicate electronic components.
- Small Flat Container: To hold isopropyl alcohol for soaking the electronic circuit board, if necessary.
- Flat Pliers: These will help you gently pry open the key fob casing without causing damage. Needle-nose pliers can be particularly useful.
- Small Flat Knife or Flat-Head Screwdriver: For carefully separating glued components inside the key fob. Ensure it’s very thin to avoid damage.
Step-by-Step Guide: Opening Your Mercedes Key Fob
Now, let’s get started with opening your Mercedes key fob. Follow these steps carefully to safely access the internal parts.
Step 1: Carefully Open the Key Fob Casing
The Mercedes key fob is designed to be securely closed, often using a combination of clips and adhesive. The first step is to gently separate the two halves of the casing.
- Extend the Key: Locate the release button or mechanism to extend the physical key blade from the fob. This will reveal a small gap in the casing.
- Insert Pliers: Carefully insert the tips of your flat pliers into the gap revealed when you extended the key.
- Gently Pry Open: Apply gentle pressure to pry the two halves of the fob apart. Work your way around the seam, being patient and avoiding excessive force. You may hear a soft clicking as the clips release.
Caution: Be extremely careful when prying open the case. Mercedes key fobs often contain a small spring mechanism for the key blade. As you pry, be mindful of this spring to prevent it from popping out and getting lost. Work slowly and methodically to avoid damaging the plastic casing.
Step 2: Remove the Electronic Circuit Board
Once the casing is open, you’ll see the internal components, including the electronic circuit board.
- Locate the Circuit Board: Identify the electronic circuit board within the opened key fob.
- Carefully Remove: Gently lift or slide the circuit board out of its housing. It may be held in place by small plastic tabs or friction.
- Battery Terminals: Pay close attention to the battery terminals. Avoid bending or breaking these delicate metal contacts. If you are dealing with water damage, immediately remove the battery if it’s still inside and hasn’t been removed already. This prevents further corrosion and potential short circuits.
Step 3: Detach the White Plastic Cover and Transponder (If Necessary)
Depending on your Mercedes key fob model and the reason for opening it, you might need to access the transponder. This is often covered by a white plastic piece. This step might not be necessary for simple battery replacement but is crucial if you’re addressing water damage.
- Apply Isopropyl Alcohol: If the white plastic cover appears to be glued to the transponder, use a Q-tip to apply a few drops of isopropyl alcohol around the edges of the plastic cover. This will help to soften the adhesive.
- Wait and Soften: Let the alcohol soak for a minute or two to weaken the glue.
- Gently Separate: Using your small flat knife or screwdriver, carefully insert the tip between the white plastic holder and the transponder. Gently pry to separate them.
Important: Be extremely gentle during this step. The transponder is a delicate electronic component. Apply minimal pressure and avoid directly pressing on the transponder itself to prevent damage.
Step 4: Removing the Transponder (If Necessary)
If you need to remove the transponder completely, for example, to clean underneath it in case of water damage, follow these steps. Again, this might not be needed for a simple battery change.
- Apply Isopropyl Alcohol Again: Similar to the previous step, apply a few drops of isopropyl alcohol around the area where the transponder is glued to the circuit board.
- Soak and Soften: Allow the alcohol to sit for a few minutes to loosen the adhesive.
- Carefully Pry Off: Using your small flat knife or screwdriver, gently slide it under the transponder and carefully pry it upwards.
Caution: Note the orientation of the transponder before fully removing it. This will be important for reassembly. Handle the transponder with utmost care as it’s sensitive to damage.
Step 5: Cleaning Oxidized Contacts (For Water Damaged Fobs)
If your key fob has been exposed to water, you might find oxidation or corrosion on the electronic contacts. This is a common issue that can prevent your key fob from working correctly.
- Inspect for Oxidation: Examine the circuit board and battery contacts for any signs of white or greenish corrosion.
- Isopropyl Alcohol Bath: Pour a generous amount of isopropyl alcohol into your small container. Submerge the electronic circuit board completely in the alcohol.
- Soak and Clean: Let the circuit board soak in the alcohol for 5-10 minutes. This will help dissolve the oxidation and displace any water.
- Gentle Scrubbing: While submerged or after removing from the bath, use Q-tips dipped in isopropyl alcohol to gently scrub away any remaining oxidation from the contacts and other areas of the board.
- Drying Time: Allow all components to air dry completely for at least 30 minutes before reassembling. Ensure no moisture remains, as this can cause further damage.
Step 6: Reassembling Your Mercedes Key Fob
Once you’ve completed the necessary steps—whether it’s just opening for battery replacement or cleaning after water damage—it’s time to reassemble your Mercedes key fob.
- Ensure Dryness: Double-check that all components are completely dry before reassembling, especially if you cleaned with isopropyl alcohol.
- Reassemble Components: Carefully place the transponder back in its position (if removed), followed by the circuit board into the casing.
- Snap Casing Back Together: Align the two halves of the key fob casing and gently press them together until they snap securely closed. Ensure there are no gaps and the casing is fully sealed.
Conclusion: Key Fob Opened and Ready for the Next Step
You’ve now successfully opened your Mercedes key fob! Whether you needed to clean it after an accidental wash or replace the battery, you have gained access to the internal components. Remember to handle all parts with care, especially the electronic circuit board and transponder.
If you were addressing water damage, allow sufficient drying time and ensure all oxidation is removed before reassembling. If you were simply replacing the battery, now is the time to insert a new battery of the correct type.
While this guide provides a DIY approach, if you are uncomfortable with any step or encounter issues, it’s always wise to consult a professional locksmith or your Mercedes-Benz dealership for assistance. Taking preventative measures, like keeping your keys away from water and extreme temperatures, can also help prolong the life of your key fob.
