Troubleshooting Your Speedometer Needle
Like most people, you probably do not give much thought to the speedometer in your car until it stops working correctly. But once the needle begins to bounce, jump, or stop moving at all, it is a problem that needs to be fixed fast. Without a working speedometer you will not be able to know if you are speeding and will be at risk for a ticket, even if it is for improper equipment. Although it usually takes a mechanic to be able to fix this problem, you can do some simple troubleshooting for the speedometer needle so you have an idea of possible causes and what to expect.
Speedometer Needle Jumps
Scenario: you are driving at normal speed when suddenly your speedometer needle shoots up by 10, 20, or even 40 miles an hour. However, you know you did not increase your speed. The needle might stay there, or it might go back to normal and repeat the jump a few seconds or minutes later. There will likely be no indicator lights flashing.
Possible problems: the speed sensor on the passenger axle may need to be replaced. The speedometer cable may be damaged or broken. If the vehicle has cruise control, the cruise control transducer could be faulty and a new one should put in its place.
Speedometer Needle is Stuck
Scenario: you are driving and suddenly the speedometer needle becomes stuck. Even when you slow down or speed up, the needle stays in the same place. If you turn off the car it may or may not go back down, and if it does, it becomes stuck again when you drive the next time. The battery indicator light may come on even though the car starts and runs fine.
Possible problems: a fuse in the fuse box may be faulty. There could have been a voltage surge that disrupted the needle as well as damaged the battery or alternator. The gauge itself may be in need of replacement.
Speedometer Needle Bounces
Scenario: while you are driving, your speedometer needle abruptly goes up by 10 miles per hour or more, then swings back down sharply. This continues the entire time you are driving, with the needle bouncing between different speeds even when you are driving steadily. The speedometer indicator gauge may come on if the car has one.
Possible problems: if it is an older car that has a cable for the speedometer, the cable may be damaged and the wire inside it broken or bent. If the vehicle has an electronic gauge, the cause may be a connectivity problem on the instrument cluster harness. The gauge itself could have stopped working.
Speedometer Needle not Moving
Scenario: you turn your vehicle on, and the speedometer needle does not move once you begin driving. You turn the vehicle off and back on and it still does not move. Other gauges work fine on the dash. The check engine indicator light may come on or there may be no indicator lights.
Possible problems: the speedometer cable is damaged or broken. The speed sensor has gone bad. The speedometer could need re-calibrating due to changes in the car or an electrical short. The speedometer may need to be replaced.
A bad speedometer needle may cost you much more than just the price for parts and labor. You may be charged with speeding if you are pulled over for going over or under the speed limit because it is not working correctly. You will have to prove you have a bad speedometer, and even then you may be cited for improper or faulty equipment. It is best not to risk this and get your needle diagnosed and get the auto repaired as soon as possible. If any of your indicator lights are on, be sure to mention that as well, as it could indicate another problem.