When was the last time you paid attention to the operation of your car’s speedometer? Perhaps you don’t even remember. Most of us tend to ignore this component of the vehicle until it starts to malfunction. When the speedometer not working in your vehicle, you are left with little possibility to travel at the preferred speed level. This can be rather concerning.
While many seasoned DIY mechanics are well equipped to handle a tune-up, or complete a brake job, not all know where to start when facing a broken speedometer. In fact, a broken speedometer is so complex in nature that some of the more complicated components of the car can be fixed easier than this.
The following guide will help you better understand the working mechanics of a speedometer as well as the many problems that this part may show.
- Function
- Common Problems
- Speedometer Doesn’t Work
- Fixing
- Repairing
- Troubleshooting
- Driving without Speedometer
- Cost
How A Speedometer Works
In the simplest words, a speedometer or a speed meter is a device that measures and displays the speed of a vehicle. For decades, a speedometer has been a standard addition to every kind of vehicle.
In some vehicles, we can find the speedometer as a large circular gauge on the dashboard. The smallest numbers are located at the bottom of the gauge. As the vehicle’s speed increases, the number increases steadily, climbing the circle. A thin needle moves in the center of the gauge and indicates the number matching the present speed. The majority of speedometers contain 2 rows of numbers, pointing to the speed in both kilometers or miles per hour.
Some modern-day vehicles come with digitized speedometers where the speed is displayed digitally. The number changes as the speed increases or decreases.
A Brief History Of The Speedometer
Speedometers aren’t the newest things in the automobile industry, but they haven’t been around since cars came into being. The absence of speedometers in the earliest vehicles wasn’t an issue as older vehicles topped out at comparatively low speeds. It was much easier for drivers to have a grip over the speed of their vehicle.
However, by the turn of the 20th century, top speeds bounced up to 30 mph, leading to an alarming increase in car accidents. In response, the speedometer was invented by Otto Schulze in 1902. The earliest speedometers were pricey and hard to find. Fortunately, by 1910, automakers started to make speedometers a piece of standard equipment in vehicles.
Early speedometers featured two gauges. One of them was found on the dashboard and made for the driver whereas the other, bigger, exterior gauge was located on the front of the vehicle so law enforcement could have a reading of the driver’s traveling speed.
Cable-Driven Speedometer
Mechanical speedometers also go by the name eddy-current speedometers as they utilize magnetic eddy currents to show the car’s speed. These analog devices are attached directly to the vehicle’s transmission shaft. In a time when electronic sensors were unknown to men, they gave drivers a dependable way to check the speed at any given time.
A cable-driven speedometer has multiple parts:
- Drive cable
- Mandrel
- Spiral gear
- Speedup
- Hairspring
- Permanent magnet
- Needle
The drive cable holds the mandrel and is wrapped about the vehicle’s transmission shaft. As the shaft turns, that rotates the mandrel as well. The opposite end of the cable is linked to a spiral gear. The mandrel’s rotation makes this gear rotate too. Connected to the permanent magnet, the spiral gear sits inside the speedup. A rotating magnetic field is created with the rotation of the magnet. This field subsequently created a drag force strong enough to pull the needle of the speedometer.
It’s the hairspring’s duty to balance out this pull, causing the speedometer’s needle’s deflection to equal the vehicle’s speed.
Electronic Speedometer
Electronic speedometers function with a vehicle speed sensor instead of a drive cable to calculate the vehicle’s speed. The sensor comprises a toothed metal disk, a magnetic coil, and a stationary detector.
The metal disk is connected to the vehicle’s transmission shaft, similar to the drive cable in a cable-driven speedometer. When the shaft turns, the disk’s teeth interrupt with the magnetic field produced in the coil, triggering the detector and transmitting a pulse to the computer of the car. The pulses are used by the computer to gauge the speed of the vehicle, how fast the engine is turning, and the distance the vehicle has traversed.
As a result, the speed of the vehicle is displayed on a digital display or conventional analog dial.
Speedometer Not Working: Common Problems
There are a handful of more probable problems your vehicle’s speedometer might start displaying. Many of these are due to wear and tear as the vehicle ages. If your speedometer is showing any of these issues, a replacement or fix may be in order.
Speedometer Not Working: Speedometer Is Dead
The speedometer can be dead due to two reasons. The most common cause within older vehicles is a break in the cable connecting the speedometer to the transmission. Cars manufactured after 1990 generally come up with speed sensors, but they are prone to crashing and stopping the display of speed readings. A more serious issue can be a bad speedometer head; an expert is required to diagnose and solve this.
An issue that is common with digital speed sensors is a malfunctioning of the component. Once they stop working, these sensors do not send any data to the computer of the vehicle. When the computer attempts to measure the road speed, there is no information to work off of, and as a result, the CEL (Check Engine Light) glows.
Changing the speed sensor does solve this issue, but, if the CEL isn’t illuminated and the speedometer shows erratic behavior or stops working totally, we suggest trying the vehicle’s cruise control. Both of them work with the same sensors so there may be a malfunction in that.
When the cruise control is working and the CEL is on, it usually indicates an issue with the speedometer itself. This may ask for a replacement of the instrument panel. On its own, an illuminated CEL is a serious problem and has to be checked as soon as possible.
Speedometer Not Working: Jerking Or Bouncing Of Speedometer
What do you do when the speedometer not working partially? The speedometer doesn’t settle on a specific reading but keeps jumping between speeds. The cause is almost always bad wiring if there is a cable system, or alternatively, a bad speed sensor. For the most part, a replacement of the wiring solves the issue. If that doesn’t work, the sensors must be re-calibrated.
Why The Speedometer Not Working
There can be multiple reasons behind a malfunctioning speedometer. Luckily, a replacement doesn’t always have to be the sole solution. Below, we provided likely problems that can be messing with the speedometer, as well as some troubleshooting tips.
Common problems include bad wiring, a faulty sensor, or dial malfunctions. Troubleshooting problems with the speedometer usually call for a change of the cable or speed sensor, based on the vehicle. Both of these repair jobs are fairly simple to perform. In fact, you can even do it at home.
Speedometer Not Working: Broken Speed Sensor
There are many purposes of a speed sensor, including regulating ignition timing and the flow of fuel, indicating the vehicle’s speed, and working the cruise control. A broken speed sensor might stop the speedometer from functioning entirely. You may also see that the vehicle doesn’t run as smoothly as before and you are starting to lose control over the cruise control.
A failed speed sensor triggers the Check Engine Light to illuminate, indicating that there is a problem.
Speedometer Not Working: Bad Wiring/Faulty Fuse
In wet conditions, the exposed wires (if any) of your vehicle can get wet, causing a blown fuse. When the speedometer’s fuse stops functioning, the speedometer can drop to zero.
Speedometer Not Working: Malfunctioning ECU
The engine control unit (ECU) can be compared to a computerized brain in a vehicle, monitoring several different aspects of the vehicle’s activity – one of them being speed. If there is an issue with the ECU, it can negatively affect the car’s ability to recognize what speed it is moving at. Consequently, the speedometer drops to zero.
Speedometer Not Working: Changes In The Car
Speedometers have been calibrated according to the diameters and radius of the factory-fitted tires your vehicle comes with. These determinants have an impact on the car’s overall functionality. If your new custom tires are larger or of different dimensions, the speedometer may be affected too. If the speedometer’s calibration is not aligned with the rate at which the tires cover ground, it can give a faulty reading.
What To Expect When Fixing A Broken Speedometer
It’s best you don’t try to repair a speedometer if you’re not skilled with your tools and know your way around a vehicle’s internal components. A mechanic will have a look at your car to determine the reason the speedometer has stopped functioning. Afterwards, the mechanic will provide a detailed report of inspection outlining the causes of the speedometer being broken along with the cost of any possible repairs.
How It’s Done
A mechanic will start by examining the vehicle with a code reader/scanner to understand and review any CEL or error codes the vehicle may have generated. By linking to the ECU of the vehicle, the mechanic derives a better concept of all failed components.
If the mechanic thinks that the problem is a failed speed sensor, they will get underneath your vehicle to locate the sensor. While at that, they will inspect the sensor as well as the corresponding wires to ensure there is no superficial damage to the component. The mechanic will proceed to remove the old, broken sensor and replace it with a new one.
In case they believe there is a bad wire or fuse to be the cause behind the speedometer not working, they will start by checking if the fuse is blown or not. If it has, the fuse will be replaced. The mechanic will also check the wires going to the speed sensor from the speedometer to make sure there are no damages.
Replacing The ECU
The entire ECU will have to be replaced if there is any problem with the unit, so pray that you don’t have to go through that. Resetting the unit can be a temporary fix at the very most; changing the ECU is the sole way to ensure it functions fully again.
After the new ECU has been installed, the mechanic will turn the ignition key into an “Auxiliary” state. This allows the ECU to start the process of running the many systems of the vehicle. Once the vehicle is on, it should start adjusting systems to ensure the vehicle runs optimally.
In every repair, the mechanic will clear out all trouble codes of the vehicle generated by the ECU with a code scanner/reader. Before leaving, they will take the vehicle on a test drive and check for the proper functioning of all systems. The speedometer should be functioning okay again.
How To Repair A Broken Speedometer
Before the repair of the speedometer, it’s crucial to determine the main reason behind the issue. Circuit integrity and speed sensor function can be validated using a multimeter or scan tool. Similarly, a bi-directional scan tool can be used to examine a vehicle’s instrument cluster.
Diagnostics
A simple visual check can also give decent results in diagnosing issues with a speedometer. Apart from the speed sensor, the corresponding connectors and wiring have to be checked for symptoms of degradation or damage. One can also inspect cluster functions if one suspects irregularities. In some cases, drivers find that the speedometer needle is jumping, or a failure is becoming an intermittent issue.
If you have found that the speed sensor of your vehicle is defective, you must replace it immediately. This simply involves taking out the damaged hold-down fastener of the sensor, extracting the component from its bore, and installing a new one.
Wiring faults are a bit harder to fix and involve finding the damaged portion of the affected circuit. This is when a replacement pigtail or harness can be bought. Alternatively, circuit repair may be possible in particular cases.
If the speedometer of your vehicle is completely defective, the instrument cluster has to be removed. This generally involves the removal of certain dash components along with their associated hardware. After that, you can buy a new/remanufactured instrument cluster. If you’re running low on funds, get the damaged cluster rebuilt.
Further diagnostics must be conducted in the event of a suspected ECU failure. Make sure to refer to the manufacturer’s guidelines for that. Though computers like these can fail from time to time, issues of this nature are somewhat rare.
Troubleshooting Speedometer Problems
Troubleshooting the problems of the speedometer has to be done in multiple steps. At first, start with removing the cables of the speedometer.
- Start by removing the engine cover and examine where the cabling goes into the main segment of the vehicle. You should see a wide black wire directed to the instrument cluster – that is the speedometer cable.
- Remove the bolt from underneath the dashboard so you have easier access to the old cable.
- In addition, take out the nut on the transmission and cable through the passage. Loosen and remove the clamps holding the cable in place on the engine compartment and transmission.
- Once the old cable has been removed from your vehicle, you need to replace it. In the adapter, repair the square side of the new cable alongside tightening the nut located on the rotating shaft.
- Afterwards, pass the new cable through the entrance and fasten the bolt. This end should be attached to the square hold of the speedometer.
- Put in the clamps you have removed earlier, and also put the engine cover back on.
Changing Speed Sensors On FWD (Front Wheel Drive) Vehicles
- The speed sensor will be found behind the engine, just over the transaxle.
- Take out the air cleaner, connecting hose, and electrical connector from on top of the sensor.
- Use a 10 mm socket to remove the bolts securing the sensor in position. Twist the sensor in order to remove it.
- Install a new O-ring to the speed sensor before cleaning the exterior sensor housing and sensor flange for reinstallation.
- Attach the new sensor in position and fasten the bolts around it. Reconnect the hose, electrical connectors, and air cleaner on the hose.
Changing Speed Sensors On RWD (Rear Wheel Drive) Vehicles
- The speed sensor on rear-wheel-drive vehicles can be found behind the transmission.
- Use a car jack to raise the vehicle up into the air.
- Take off the wheels.
- Detach electrical connectors linked to the sensor as well as the bolts securing the sensor in place. Use a socket for the latter.
- Take out the old sensor carefully and install a new one in its place. Make sure you change the O-ring before installation. Connect the electrical connector to it and fasten it.
Can I Still Drive Your Car If My Vehicle’s Speedometer Not Working?
Technically speaking, you can drive a vehicle with a malfunctioning speedometer. But we don’t recommend that at all. Without an alternative plan in mind, you will fail to register the speed at which the vehicle is moving. Not only is this dangerous but you are significantly increasing the risk of getting in trouble with law enforcement for violating driving laws.
Simply put, the chances are very thin that you will slime your way out of a speeding ticket simply because the speedometer was not working. In any event, a broken speedometer must be addressed as soon as possible.
Can I Use My Phone As A Speedometer Instead?
GPS is a common feature in all modern smartphones. As a result, your device can accurately recognize its own location and decrease car insurance in addition to its speed of travel. A few innovative minds have realized this niche and explored it, developing speed-tracking applications to help you keep track of location and speed without the amenities provided by your vehicle.
In the event of a failure of the speedometer, a speed-tracking application can be used to keep tabs on the speed of the vehicle. Fortunately, many of these apps are free to download and use, so it’s best to download one immediately the moment the speedometer starts displaying signs of failure.
However, it’s important to note that these kinds of apps are not 100% accurate. Therefore, only consider these applications as a fallback option, nothing permanent. Your primary concern should be resolving the speedometer’s issue.
Cost Of Fixing A Speedometer
The cost of repairing a vehicle’s speedometer is quite variable and mainly dependent on the main cause of the issue at hand. Needless to say, the cost varies for people who are choosing a DIY repair versus those who opt to get a shop or repair facility to handle it for them.
The most common issues related to speedometers not working in a vehicle can be traced back to the failure of speed sensors. Most shops ask between $100 to $250 for speed sensor replacement (in-house). However, the costs are significantly lesser for DIY repairs, as the driver will be absorbing only the price of the sensor itself. Sensors of this nature go for as little as $25 to $40 on the market.
When the problem diverts from the speed sensor and an instrument cluster failure is what you are dealing with, the repair can be much more expensive. A simple rebuilt instrument cluster can go for as high as $400. With the price of a new instrument cluster/speedometer at an all-time high, drivers pray they never have to replace this part.
Bottom Line
On the bright side, not all speedometer issues require replacement jobs. It is determined by the cause. In case the problem is with the dial, the dial alone can be replaced. Problems with the built-in computer do need replacement. Thus, it is crucial to take your car to a licensed professional and have them run a total diagnostic test when the vehicle’s speedometer not working. Proper diagnosis and troubleshooting can save you a lot of time and money.
Approved Tools
These tools have been tried and tested by our team, they are ideal for fixing your car at home.