Many owners of the 1999 Mercedes E320 wonder about the role of the battery in their key fob, especially when issues arise. It’s a common misconception that a dead key fob battery will prevent your car from starting. Let’s clarify how your Mercedes key fob truly operates and what the battery is actually for.
Your 1999 Mercedes E320 key fob is a sophisticated piece of technology. Interestingly, the battery inside the fob is not required to start or drive your vehicle. The magic behind starting your E320 lies in the Electronic Ignition System (EIS). When you insert your key fob into the ignition, the EIS activates induction coils around the key opening. These coils generate an electrical current within the fob itself. This induced current powers the fob’s internal circuits and, crucially, the infrared (IR) emitter located at the end of your key fob.
This IR emitter then sends a signal to the EIS, which in turn activates the starting and ignition systems. This ingenious system means you can start and drive your 1999 Mercedes E320 even if the key fob battery is completely dead. If your car is failing to start, it’s highly unlikely to be related to the key fob battery. A more probable cause would be issues with fuses or relays within your vehicle’s electrical system.
So, if the battery isn’t for starting the car, what is its purpose? The key fob battery exclusively powers the Radio Frequency (RF) circuit. This RF circuit is responsible for the remote lock/unlock system, controlling your doors, trunk, and alarm system. A dead key fob battery will mean you lose the convenience of remote unlocking and remote alarm deactivation. You’ll need to manually use the metal key blade to unlock your car. Be aware that using the metal key to unlock the door will likely trigger the alarm until you disarm it using the interior lock button.
Furthermore, the key fob battery powers the “convenience system.” This system allows you to operate features like remotely opening and closing windows and the sunroof by pointing the IR emitter at the small black sensor on the exterior door handle. By holding down the unlock button while pointing at the door handle, you can unlock the car, roll down all windows, and open the sunroof. If your E320 is equipped with ventilated seats, holding the unlock button may even activate the driver’s seat ventilation. Conversely, holding the lock button while pointing at the door handle will close everything.
In summary, while a key fob battery replacement might be necessary to restore remote functionalities and convenience features of your 1999 Mercedes E320, it’s not related to the car’s starting mechanism. If you’re experiencing starting problems, focus your troubleshooting on other potential electrical issues like fuses and relays before assuming it’s a key fob battery problem.
