Speedometer Light Not Working: Reasons and Best Fixes

Getting caught with malfunctioning speedometer lights in the middle of driving is so alarming. It is disorienting and dangerous not to be able to monitor your speed. When you are riding along a speed-restricted road, it could be frustrating. And continuing to drive in this situation means risking you & other vehicles around you.

Dash electrical problems highlights

• Level of urgency:low
• DIY inspection:impossible
• DIY repair:impossible
• Can you drive?yes
• Price for repairs:$250 - $550
• Symptoms:glitchy dash, functions not working, no lights, no data
• Ways to solve:try disconnecting the battery for some time, take it to a professional

What Happens When the Speedometer Light is Not Working?

The malfunctioning speedometer light can cause different problems in your car.

What does a malfunctioning speedometer look like? It could be dead, flickering, or dimming. These faulty displays would affect the way you drive.

First, the driver cannot visibly gauge their vehicle speed. It will not connect to the vehicle's electrical system. The short circuit may affect other electrical components.

For this reason, you need to know why this happens on your speedometer light.

Reasons Why the Speed light is Not Working

1) Activated dimmer switch

If you notice your speedometer light has been dimming, you may mistake it for dying sooner. It could have been caused by accidentally bumping the dimmer switch. You may mistake it for your car battery dying, but it is just the dimmer switch. The speedo dash dimmer switch adjusts the brightness of the dash lights. Therefore, it must have been pressed and adjusted to dimmer settings.

You can test if it is the culprit by adjusting the dimness level through the dimmer switch.

2) Taillights or headlights are out.

Although these lights are far from the lights in your instrument cluster, it makes sense when your lights are out. If all the lights in your dash are dim, check the taillights or headlights. These lights should be out when all your dash lights are out. Most vehicles today share the same electrical line or fuses. If all of them are out, your fuse is in good condition.

If the taillight or headlights are on, then the problem must be in the circuit or fuse.

3) Car battery dying

A weak car battery does not only affect speedometer lights but all the other lights as well. A dying car battery will not have enough power to supply the electrical systems in the vehicle, including the lights in your gauge clusters.

Since it doesn't provide enough power, the electricity could only convert it to little brightness. You can also notice it with other systems relying on electricity. But the best way to diagnose a weak battery is to test its voltage with a multimeter.

A dying battery needs replacement.

4) Broken or loose wiring connection

Faulty wire connections can affect the performance of your vehicle's speedometer light. These connections prevent the speedo dash light from turning on or causing dimming and flickering. They will deliver intermittent electrical supply or none at all.

Wiring connections can be poor when exposed to elements such as moisture. They get corroded over time and affect the delivery of electricity.

Aside from that, rodents can get into your car and chew wiring harnesses, including the ones used in your instrument cluster. If your wires rub against each other, they could burn or break.

To diagnose the issue, you can inspect the terminals and wires.  Check for any signs of corrosion, breaking, or damage. Replace loose or broken connections at once to illuminate the backlight behind your speedometer.

5) Blown fuse

A fuse box encloses all routed electrical components in your vehicle, including the wires from your speedometer light. The fuse protects these components from sudden electricity surges. Without a fuse box, a sudden surge of electricity could damage all other electrical components. But with too much electricity flowing on a circuit, the fuse could blow.

However, a blown fuse will interrupt the electric connection. Find the fuse box connected to your speedometer light and look for a fuse with visible burns. Replace it as soon as possible.

6) Car changes

If your car has gone through upgrades, modifications, or changes, it can affect the performance of the speedometer dash light. The problem with some modifications is they might cause the lights not to illuminate if the process has touched the speed sensor, wirings, or the speedometer itself.

Aside from that, you must have an updated gauge cluster compatible with the changes made, so your speedometer lights can communicate well with the upgraded systems.

If your car has gone through changes and the speedometer or dash light stops illuminating, you'd have to go through the steps above to find which causes the problem. This process would be easier if you use an OBD scanner to see the trouble codes.

7) Faulty Bulb

It is unlikely to burn out your bulbs because they should last a lifetime. Most modern cars utilize LED lights to illuminate gauge clusters, including your speedometer light. You can easily spot them as they tend to leave a dark spot in the instrument cluster. However, you cannot simply replace these lights because it requires expertise and professional skills.

8) ECU Problems

The ECU controls most systems and components in the vehicle, including the speedometer light. It sends the signal of when to not or to turn on. But when it is malfunctioning, it may send the wrong or may not send any signal to illuminate.

The ECU could have many reasons it is malfunctioning. First, it could be an issue with electrical components such as sensors or wires. It could also be because of software issues. These issues can interrupt the communication between the speedometer light and the ECU.

The only fix to this is to bring it to your trusted service technician for accurate diagnosis, replacements, or software updates.

9) Malfunctioning instrument cluster

Having a malfunctioning instrument cluster can be very dangerous. This can cause the speedometer to dim, flicker, or not illuminate. It will not only make it difficult for the driver to read the speedometer but all the other gauges as well.

The gauge cluster may malfunction due to electrical issues like faulty wiring, weak battery, or defective speedometer. A defective speedometer will display incorrect readings or not display the gauge at all.

You can start inspecting the connections: from the wires to the harnesses and the light bulbs. Use a multimeter to test the light bulb and wirings for electric continuity. Repair the affected component if replacing is not necessary.

10) Defective Speedometer

Like the ECU and gauge cluster, a defective speedometer will have trouble communicating the display lights on the speedo dash. A faulty speedometer is a result of bad wire connections, electrical components, or the speedometer assembly.

Inspect the connections between the speedometer and the speedo light. If there is no corrosion or poor connection, the problem is in the speedometer. It will need replacement in this case. Purchase a speedometer compatible with your vehicle's device. And make sure that a professional will do the replacement.

11) Defective speed sensors

Defective speed sensors can cause the speedometer light not to work properly. The speed sensor connects with the speedometer. It reads the vehicle speed and sends this data to the speedometer. But if the speed sensor has been damaged, it cannot send accurate data. This will affect the performance of the speedometer light.

The display will not show the correct reading when the defective sensors read inaccurate data. Sometimes the speed sensor could read 0 mph even if the vehicle is moving. Sometimes, the sensor will not send any data at all, causing the speedometer to malfunction and not illuminate.

How to Diagnose a Malfunctioning Speedometer Light?

• Before opening the instrument cluster, check first the dimmer switch. You may have bumped into the button a few times before it adjusted to dim light.
• Check your taillights or headlights to see if they illuminate or stop working at the same time. They most likely share the same fuse box.
• Check the fuses for possible burns.
• If you can't find the faults by doing the steps above, bring your vehicle to your trusted service shop. They will scan your instrument panel for trouble codes.

Final Thoughts

Remember that any repair attempt on the instrument cluster needs expert hands. Because you are dealing with gauges, prying it up open may damage its wirings and sensors, which can affect the entire performance of the device and your vehicle's computer.

Additionally, do not attempt to drive without the display on your speedometer. You cannot monitor your speed at this point. You will not know if you are driving too fast or are committing a traffic violation. Even if you had to go slowly, you may cause unnecessary obstruction for other vehicles and traffic.

If you're speedometer dash light is not working, bring it to your service shop now.