Speedometer Not Working – Causes and How To Resolve It

Speedometer not working can make drivers uncomfortable and, worse, unsafe. It can also be alarming, especially if you are a first-time driver.

However, you don’t need to worry because, in this article, we’ve covered all possible reasons why this can happen and how to fix it. Keep reading!

What Is the Reason Why Your Electronic Speedometer Is Not Working?

The reason your electronic speedometer is not working includes faulty wiring, faulty instrument cluster, and vehicle alterations. In addition, a malfunctioning ECU, low transmission fluid, and a faulty speedometer wire are some of the other common reasons why your speedometer isn’t working.

Faulty Wiring

Faulty wiring can be a reason why your cable-driven speedometer isn’t working. The wiring assists the electrical circuit that supplies electricity to the instrument panel. When this wiring is disconnected, frayed, or faulty, it can lead to a complete or disconnected loss of signals from the vehicle’s sensor to the speedometer.

The speed sensor measures the rotational speed of the wheels and sends these impulses to the speedometer. If the wiring is broken or faulty, these impulses might not reach the speedometer. Thus, a dysfunctional reading can lead to a completely nonfunctional or broken speedometer.

In addition, bad wiring can introduce electromagnetic interference, which distorts the signals and impacts the speedometer performance.

Bad Instrument Cluster

A damaged gauge cluster is another major reason for a broken speedometer. The gauge cluster houses several components, including the speedometer, and it displays the information from the components to the central driver. If the cluster begins to malfunction, it can impede the accurate display of speed.

Inside the gauge cluster are electronic components, such as stepper motors or speed indicators, which convert signals from the vehicle’s speed sensors into the speedometer’s readings. If any of these components fail or become damaged, the speedometer may stop functioning or display inaccurate readings.

In addition, there can be an electrical issue within the instrument, such as a blown fuse or faulty circuit board, which can cause the speedometer to fail.

Components Alterations

Altering components of your car is one of the reasons why your speedometer stops working. For instance, changing the indicator in your car to a different one may lead to an incorrect reading. This is because the speedometer is calibrated to the car’s original components. Once you start to change them for newer ones, the speedometer will need to be recalibrated, which can slow it down.

Also, changing the gear ratio, such as installing different axle ratios, can impact the relationship between the engine’s RPM and the wheels’ rotational speed. Thus, the speedometer may not display the correct speed due to the altered driving dynamics.

Additionally, adding aftermarket performance parts or accessories, like performance chips or tuning modules, can affect the speed sensor’s data interpretation, causing the speedometer to display incorrect speeds.

Distorted ECU

A malfunctioning Engine Control Unit (ECU) can be another culprit for a speedometer that isn’t working. The ECU manages various aspects of the vehicle’s performance, including interpreting data from the speed indicator to determine the speed of the vehicle. The speed indicator, located on the transmission or wheel hubs, measures the rotational speed of the wheels and sends electrical signals to the ECU.

The ECU then processes this data and transmits the speed information to the speedometer to display the vehicle’s speed on the instrument cluster. Once the ECU develops a fault, it may fail to process signals from the vehicle speed sensor or even fail to send the data from the broken speed sensor to the speedometer.

Worn-out Speedometer Wire

Another culprit of nonfunctional speedometer issues is a worn-out speedometer wiring. In older vehicles and some modern ones that use mechanical speedometers, the speedometer wiring connects the transmission’s speed indicator to the speedometer gauge on the gauge cluster.

As the vehicle moves, the transmission’s speed indicator rotates, and this rotational motion is transmitted through the speedometer cable to the gauge. Inside the speedometer, the cable’s rotation is translated into the vehicle’s speed and displayed on the gauge.

If the cable becomes damaged, worn out, or disconnected, the rotational motion from the speed sensor cannot reach the speedometer accurately. The speedometer may fail to show any reading or display an incorrect speed.

Low Level of Transmission Fluid

The transmission fluid serves multiple purposes, including providing hydraulic pressure to engage gears and cooling the transmission system. In certain designs, this fluid may also act as a medium to transfer rotational motion from the transmission’s output shaft to the speedometer sensor. When the fluid level is low, the rotational motion may not be effectively transmitted.

As a result, the speedometer may display inaccurate readings or not function at all. Also, low fluid levels can mean insufficient lubrication of some parts. This can lead to a greater propensity for overheating, invariably damaging the transmission, the speedometer sensor, and other components.

Solutions to a Speedometer Not Working

The solutions to a speedometer not working are to determine the integrity of the speedometer wire, inspect and fix the speed indicator, test for electrical draw, and refill the transmission fluid. You can also switch out broken mechanical components and closely examine the instrument cluster to fix it.

Evaluate the Speedometer Cable’s Integrity

Evaluating the integrity of the speedometer wiring can help fix a defective speedometer. First, you need to check the speedometer wire for signs of damage, such as fraying, kinks, or breakage. You also need to assess both ends of the cable for secure connections.

To examine it closely, remove the cable from both the speedometer gauge and the speed indicator on the transmission. With the cable detached, manually rotate both ends while observing its movement. The cable should rotate smoothly without resistance or binding.

If the cable appears sticky or dry, you might need to apply ample lubricant to ensure a smooth operation. Attach one end of the cable to a handheld electric drill and the other to the speedometer gauge for better evaluation. Turn on the drill to spin the cable and verify if the speedometer responds with correct readings. If it is incorrect, you might need to replace it.

Inspect and Repair the Defective Speed Sensor

You can ensure your damaged speedometer works again by fixing the sensor. Identify the bad speed sensor’s location, typically on the transmission or wheel hub. Then check for any visible damage, corrosion, or loose connections. You might also need to use a multimeter to measure the sensor’s electrical output while the vehicle is in motion.

You might need to ensure the readings you get match the expected values for different speeds. If they do not match it, the sensor is faulty, and you need to replace it with a new one that is compatible with your vehicle. After replacing the faulty speed sensor, check for error codes and clear any using an OBD-II scanner.

Examine Wiring Connections

By inspecting the wiring and electrical connections, you can identify and resolve issues that may disrupt the transmission of data to the speedometer gauge. First, check for any visible damage or fraying in the wiring that connects the speed indicator to the speedometer gauge.

Then go ahead to ensure all electrical connections related to the speedometer system, including plugs and terminals, are securely attached and free of corrosion. If you find any damaged wires or faulty connections, repair or replace them as needed.

You might also need to test the speedometer to ensure it displays accurate readings while driving and to ensure that only the sensor is faulty.

Test for Power Usage

You might need to test for the electrical draw if your speedometer is faulty. Start by turning off the engine and all electrical accessories to do this. Also, ensure the vehicle is in a parked and safe position. You then safely disconnect the vehicle’s battery to prevent any electrical accidents while performing the test.

Following all these safe measures, locate the speedometer circuit and trace the wiring from the speed indicator to the speedometer gauge. Set the multimeter to measure amperage and observe the multimeter reading to measure the electrical draw of the speedometer circuit.

If it exceeds the acceptable range, an electrical issue may affect the speedometer’s operation. You can identify and address electrical problems from these test results, such as a short circuit, excessive resistance, or malfunctioning component.

Switch Out Damaged Mechanical Components

For older vehicles where the speedometer is mechanically driven, switching out broken mechanical components can help fix a malfunctioning speedometer. To begin this assessment, determine which mechanical component is causing the speedometer problem. It could be the wiring, gear, or any other related part.

You can then carefully disconnect and remove the broken mechanical component from the speedometer system. Examine it for any signs of damage, wear, or breakage. If it is damaged, replacing it with a new one that matches the manufacturer’s specifications and the vehicle’s make is important.

Top-up the Transmission Fluid

While fixing the speedometer by topping up the fluid level is rare, it can work if the issue is related to a low transmission fluid level or the fluid is dirty. First, inspect the fluid level using the dipstick to determine if it is below the recommended level.

Once you find that it is low, add the appropriate type and amount of fluid, as specified in the vehicle’s owner’s manual, to bring it to the correct level. Then, you need to test the vehicle and verify if the working speedometer now displays accurate readings.

Closely Inspect the Instrument Cluster and ECU

While this fix is a last resort as it is arduous and stressful, it can be a solution to your defective speedometer. After you observe the check engine light, you can either reset this component or install a new one. However, resetting it is temporary. It is important for the new gauge cluster and ECU to be installed by expert automobile technicians.

FAQs

Can You Still Drive With a Defective Speedometer?

Yes, you can still drive with a defective speedometer. However, it’s not advised because you might incur fines if found doing so. Also, it might affect the configurations between the speedometer and odometer. This is mostly common in cars where both components are connected.

What Is the Cost of Fixing a Speedometer?

The cost of fixing a speedometer is between $20 to $245 if you fix it yourself and $200 to $300 if you contact a mechanic. The speedometer repair cost varies from car to car and depends on the degree of repair your vehicle needs.

Conclusion

It can be scary to have a defective speedometer, but you don’t need to panic now that you have read this article.

Here are our concluding thoughts on the main points in the article:

• Your speedometer stopped working for reasons like faulty wiring, faulty gauge cluster, and vehicle alterations.
• A damaged ECU, low transmission fluid, and worn speedometer wire can also be reasons why your speedometer doesn’t work.
• The solutions to a bad speedometer include determining the integrity of the speedometer wire, inspecting, and fixing the speed indicator, testing for electrical draw, and refilling the transmission fluid.
• You can also switch out broken mechanical components and closely examine the gauge cluster to fix it.

With the knowledge from this article, you should be able to troubleshoot and fix the problem once you discover the vehicle speedometer has become faulty.