The most common causes of speedometer problems are damaged rear facial gears and damaged engine speed sensors. Electrical problems within the speedometer itself also cause speedometer malfunctions. In other cases, a damaged gearbox cable is the root of the problem.
Speedometers have an important gear mechanism behind their dial faces. If this delicate mechanism incurs damage, replacement is the only option. Speedometer gears are inexpensive and available at automotive stores. Individuals who feel comfortable removing their vehicle's dashboard paneling and disconnecting its battery often elect to save on labor fees by replacing the speedometer gauge themselves. Cars Direct warns, however, that home repairs may void the vehicle's warranty.
Other speedometer problems require professional diagnosis with electronic sensor test equipment. For example, a speedometer that behaves erratically or stops functioning completely may be a symptom of a more serious problem, such as a broken engine speed sensor. This issue requires professional evaluation and repair. Other symptoms of this condition include sporadic activation of the check engine light and intermittent braking difficulties.
Vehicles without working speedometers automatically fail their annual inspection and are unsafe to drive. When speedometer problems appear, the best course of action is immediate inspection by a certified auto mechanic.