What are the reasons for the tachometer not returning to zero?

[MacElliana]

The reasons for the tachometer not returning to zero are: 1. Fault in the tachometer itself; 2. Fault in the power supply or grounding circuit of the tachometer; 3. Fault in the data bus of the tachometer; 4. Blown fuse; 5. Foreign object stuck inside the tachometer, preventing movement; 6. Fault in the vehicle's mileage sensor. The tachometer is a tool used to measure the speed, linear velocity, or frequency of a motor. Its working principle is: it operates based on magnetic principles, receiving pulse signals generated when the primary current in the ignition coil is interrupted, and converting this signal into a displayable speed value. Methods to address the tachometer not returning to zero: 1. Check the working condition of the tachometer; 2. Open and clean any foreign objects inside the tachometer; 3. Replace the tachometer with a new one; 4. Check for any faults in the circuit.