How to Replace the Battery in an Older Mercedes-Benz E400 Key?
3 Answers
Here are the detailed steps to replace the battery in a Mercedes-Benz E400 key: 1. Locate the switch on the back of the key fob and pull the top part outward to remove the internal metal mechanical key, revealing a small notch. 2. Use a flathead screwdriver or similar tool to pry open the key fob cover along the notch. Once a gap appears, you can manually separate the cover. 3. After opening the key fob cover, remove the old battery and replace it with a new one, paying attention to the correct polarity. 4. Reattach the key fob cover and reinsert the mechanical key to complete the process.
Changing the key battery is quite simple, and I often help friends with this task. The older Mercedes-Benz E400 key usually comes with a small remote shell that uses a CR2032 coin cell battery. First, take a small tool, like a flathead screwdriver or a plastic pry bar, and carefully insert it into the edge gap of the key. Gently pry open the shell without using too much force to avoid scratching the plastic. Then, remove the old battery, noting the orientation of the positive side (marked with a plus sign) facing up to avoid installing it backward. Simply place the new CR2032 battery in the same position. Finally, close the shell and press the buttons a few times to test if the lock/unlock functions work properly. Key batteries typically last 1 to 2 years, and when the power is low, the remote range will shorten, so regular checks can prevent the embarrassment of a dead battery when driving. Before starting, it's advisable to search for a video tutorial online for a demonstration to be extra safe. If the battery cover is difficult to open, don't force it—seek help from a professional shop for a more secure solution.
Last week, my car key remote stopped working properly, so I figured out how to replace the battery myself, and it worked great. For this older Mercedes model, there's a small slit on the back of the key—just use a hard card or your fingernail to pry it open, revealing the battery compartment. Take out the old CR2032 battery and buy a new one at the supermarket for just a couple of bucks. When installing, make sure the battery's positive and negative sides are aligned correctly. You should hear a click when the new battery is pressed in securely, then just snap the cover back on. After replacing, test the car's ignition and remote buttons immediately to see if they're working again. Remember to keep the key away from water or direct sunlight—storing it in a bag daily helps protect the battery and extends its life. I usually opt for big-brand batteries for better quality assurance. Simple, easy, and saves both money and time.
