Why does the speedometer needle fluctuate up and down?

[DeDelaney]

Speedometer needle fluctuations are usually normal as long as the amplitude isn't particularly large. How speedometers work: The speedometer consists of a permanent magnet fixed to the drive shaft, an aluminum cup with shaft and pointer, a housing, and a dial firmly attached to the casing. When not in operation, the aluminum cup, under the action of a spiral spring (hairspring), keeps the pointer at the zero position on the scale. Types of speedometers: Common vehicle speedometers are typically divided into three types: purely mechanical, electro-mechanical, and fully electronic. The purely mechanical type has basically exited the market, the electro-mechanical type is most widely used, while the fully electronic type is typically used in the bus industry.