What is the reason for the button still being lit after the vehicle is turned off?
2 Answers
Due to a short circuit between the panel backlight control circuit and the power supply. Solution: Check whether the ON/BK lighting control high level at pin 12 of CON1 and the Adj dimming voltage at pin 13 are normal. If both are normal, test the voltage at each pin of the drive circuits U1 and U2. Inspect the external protection sampling circuits of U1 and U2. It was found that the resistance value of external R12 at pin 1 of U1 had increased from the normal 300k to 500k, causing the detection voltage OVP at pin 1 to be too low, which activated the undervoltage protection circuit inside U1, forcing both U1 and U2 to stop working simultaneously. After replacing R12, the fault was resolved. Principle of the backlight drive control circuit: The main and auxiliary drive control circuits are composed of two RT8566IUI (U1 and U2). Each circuit consists of a drive control and a boost output section, which respectively supply power and adjust the current for 8 LED backlight strings. The main drive control circuit RT8566 (U1), MOS switch tube Q1, energy storage inductor L1, freewheeling diodes D1 and D2, and filter capacitors EC2, C5 to C8 form the circuit. After the remote control is turned on, the circuit starts working, boosting the VIN power supply to over 40V to power the LED1-LED8 backlight strips, while also controlling the current equalization of the LED strips.
I often encounter the situation where the buttons remain lit after the engine is turned off. This is usually due to the car's delayed shutdown function design. For example, some lights will automatically turn off a few minutes after you turn off the engine, providing illumination for convenience so you don't have to get out of the car in the dark. If you accidentally leave the reading light switch on, it will continue to consume power. Another common reason is that the car door or hood isn't closed properly, or the key is still in the ACC position and not removed, causing the system to think you're still operating the vehicle and not cutting off the power. Hardware failures can also be the cause, such as a stuck control module or a short circuit in the wiring. I've personally experienced a dead battery because the lights didn't turn off. It's recommended to check the dashboard and switch status more carefully after turning off the engine next time. If this issue persists, it's best to visit a repair shop to have the circuit checked with a diagnostic tool to avoid being stranded on a long trip.
