What Causes the Engine Tachometer to Return to Zero?

[AliyahDella]

It may be due to a malfunction in the vehicle's instrument cluster speedometer. Here is additional information: Reasons why the engine tachometer does not move: Possible causes include a faulty wheel speed sensor, a malfunctioning mileage sensor, or foreign objects stuck inside the gauge. The engine's rotational speed affects the number of work cycles per unit time or the effective power output of the engine, meaning the engine's effective power varies with different speeds. Tachometer rated power and rated speed: The effective power and corresponding speed specified on the engine's product label are referred to as the rated power and rated speed, respectively. The operating condition of the engine at rated power and rated speed is called the rated condition. The rated power is not the maximum power the engine can produce but rather the maximum permissible effective power determined based on the engine's intended use. For the same engine model, the rated power value may differ depending on its application.

[OAaliyah]

I've been repairing cars for over a decade and have encountered many cases where the tachometer drops to zero. The most common issue is a faulty crankshaft position sensor, which is responsible for measuring engine speed signals to the dashboard. Wiring problems also frequently occur, such as aging wire harnesses with poor contact or grounding shorts, especially prone to rusting in rainy and humid conditions. Blown fuses are another prime suspect - simply replacing them with the correct model usually solves the problem. Dashboard malfunctions are relatively rare, but older vehicles may require complete dashboard replacement if the circuit board fails. When the tachometer suddenly drops to zero while driving, stay alert. Sometimes the engine is still running - listen carefully to assess the situation without panicking. Pull over promptly for inspection or call a tow truck to prevent engine damage.

[ValeriaAnn]

Last time my car's tachometer dropped to zero, it gave me quite a scare. As an ordinary driver, I decided to learn how to check it myself. First, open the fuse box and look for the fuse labeled 'engine compartment', pull it out to see if it's broken. If it's blown, just replace it with a fuse of the same specification. Then check if the sensor connector is loose or corroded, and clean it if you can. Wiring faults like short circuits are hard to handle on your own, so it's better to let a professional use a multimeter to measure the resistance. Develop a habit of regular maintenance, such as checking the wiring harness connectors annually to prevent water accumulation. Spending a little money now can prevent major faults later.

[BradleyRose]

From a safety perspective, a tachometer dropping to zero means you lose real-time awareness of engine status, significantly increasing driving risks. Signal loss is often caused by sensor failure, wiring breaks, or instrument cluster malfunction. While engine stalling isn't problematic, continued operation without RPM indication risks overspeeding and engine damage. Upon noticing this anomaly, immediately pull over, turn off ignition, restart to test. If unresolved, seek professional diagnosis. For prevention, avoid excessive water exposure during car washes and regularly clean around sensors.