What does the AMS button in the car mean?
4 Answers
AMS in the car stands for Alternator-Management-System, referring to the power management system. Below is more information about AMS: Function: Cars equipped with the AMS power management system allow the generator to measure the battery status via current sensors. It adjusts the generator's load based on driving conditions, controlling battery charging and discharging to improve fuel efficiency and extend battery life. Power Distribution: The AMS system manages power distribution, optimizing the engine's electrical supply. During Driving: Dynamic power management allocates the current generated by the generator to various electrical components as needed. When the generator produces more current than the electrical components consume, it regulates and supplies the excess to the battery, ensuring optimal charging.
I've been driving a taxi for over twenty years, pressing the AMS button every day to listen to crosstalk for amusement. Actually, this button is a quick media switch key—just poke it while driving to cycle through songs from USB, radio, Bluetooth, or your phone. Yesterday, I even had a passenger who didn't know how to use it and ended up switching the radio to their phone's navigation voice. Some cars have the USB port inside the armrest box, and pressing the AMS button shows a small icon of the current mode on the dashboard, which is quite handy. But older cars react a bit slower; pressing it too quickly can cause it to freeze with no sound, and in that case, just restarting the engine fixes it.
As an electronic engineering major, I have studied the underlying logic of the AMS button. It corresponds to the Auto Media Switch protocol, with its core being a multi-channel audio switcher. For example, when you press the AMS button while connected via CarPlay, the system automatically polls three data sources: USB, AUX, and iPod. German cars typically connect it to the BCM (Body Control Module), while Japanese cars directly link it to the infotainment unit. Be aware that aftermarket multimedia systems may disable the original AMS function, which I encountered when upgrading my audio system.
The AMS button is my go-to for playing children's songs when driving with kids. It's the one with the musical note icon on the lower right of the steering wheel. Last week while dropping my child off at kindergarten, the USB playlist suddenly switched to my husband's financial news broadcast from the night before, giving me quite a start. I later learned that holding the AMS button for three seconds locks the current audio source. Now I always double-check that the USB is securely plugged in before heading out with my child, since I can't spare a hand to adjust the center console while driving.
