Speedometer Buyer's Guide
- A speedometer measures your car’s speed.
- There are two types of speedometers, and both work differently from one another. Mechanical speedometers take advantage of springs and electromagnetic waves, while electrical speedometers make use of magnetic sensors.
- The technology for the speedometer was invented in the 1900s, however, it was only implemented as a standard a decade later.
- It’s not safe to drive with a broken speedometer as knowing what speed you’re going is integral to driving. This is especially important when you’re driving in the suburbs, or on an uneven road.
- Have your car checked if you feel like your speedometer is faulty, as either your vehicle sensor is broken, or your car’s engine control module is acting up. Both are valuable components for your car and should not be taken for granted.
- Find the perfect fit for your car’s replacement speedometer at CarParts.com using the site’s search filters that effectively narrow down your search specific to your car’s model year and make.
Going fast has always been something people love to do. It’s as if there’s something polarizing about speed and what it’s all about. Humans are so addicted to speed, that there was a tool devised in order to measure it as we move. This tool is called the speedometer. Of all the tools that you may see displayed on your dashboard, the only legal requirement that’s consistent around the world is the speedometer.
How Does a Speedometer Work?
Speedometers are often regarded as very simple tools due to the fact that one can see them installed on any type of vehicular land transportation system. The processes on how one works, however, has been becoming increasingly complex as time moves forward. Certain technological advancements allow the improvement of the accuracy of the tool while cutting costs to produce it. This makes its installation more favorable to both the automaker and the consumer.
The common knowledge is that a speedometer measures speed, however, what’s less known is how. To determine this, it’s important to note that there are two types of speedometers available in the market as of writing this post, mechanical speedometers, and electric speedometers. What this section will point out is how the differences between the two go far and beyond aesthetics and display.
Mechanical speedometers work with a very technical set of components along with the use of electromagnetism. It’s a complex mixture of simple technologies that work together hand-in-hand to produce a measurement of speed. What happens is that when the wheel of your car turns, the speedometer cable, powered by the driveshaft, turns as well.
As the speedometer cable spins to the speed of the wheel, a speed cup (which moves the dial display on the dashboard) found along the same cable containing a small magnet spins. As the magnet spins, it creates eddy currents which, in turn, affects the speed cup.
A hairspring prevents the speed cup from moving freely, effectively restraining it from spinning 360 degrees. The movement is then reflected on the speedometer, pointing to the corresponding value of speed.
Electronic speedometers or digital speedometers work very differently from mechanical speedometers. Small magnets attached to your vehicle’s driveshaft sweep past smaller magnetic sensors positioned in short distances from each other. Each time the magnets pass the sensors, they pulse briefly with electrical current.
An electronic circuit counts the pulsations per certain amount of time and calculates it into a measure of speed to be displayed electronically on the display on your dashboard.
In cases where the electronic speedometer displays your speed through a dial like a mechanical speedometer, the electronic circuit drives a highly controllable electric motor (called a stepper motor) that rotates the pointer through an appropriate angle.
History of Speedometers
During the first emergence of the speedometer in the 1900s, it was merely an optional add-on to your vehicle. Much like present-day luxuries, such as dual air-conditioning and power windows. However, during the 1910s, it became a standard in all vehicles, whether budget or luxury. This is due to the fact that safety and security functions were needed to be kept in check in order to lessen road accidents and regulate vehicles.
Even before the establishment of the National Highway Traffic Safety Administration (NHTSA) in 1970, regulations have been set in place due to the massiveness of cars and the dangers they bring about to pedestrians.
Is it Safe to Drive With a Broken Speedometer?
No. For one, it leaves the determination of your speed to ‘gut feel,’ and no matter how accurate you think your gut feel is, it’s not as accurate as a working speedometer. Driving with a faulty speedometer can get you pulled over due to incorrect speed reading.
The worst thing would be that you ride over a terrain not meant to be driven over at the speed you’re currently going at, unknowingly causing damage to your car’s undercarriage and wheels. Before repairs get nastily expensive, it would be better to address a faulty speedometer right away instead of waiting for it to cause more damage.
What Are the Causes of a Faulty Speedometer?
Sometimes, a faulty speedometer doesn’t mean it’s broken. If it’s registering some speed instead of no speed at all, or you feel as if the speed it’s displaying is wrong, here are some of the possible causes:
A faulty vehicle speed sensor
Vehicle speed sensors are present in electronic speedometers. These are the ‘smaller magnetic sensors’ that were previously mentioned. Aside from being used for reading a speedometer, these are used by your car’s cruise control and anti-lock brake system (ABS).
Electrical or computer problems
Cars have electronic components that compute data. When these computers are faulty or are experiencing a problem, the computations might not come out right or they might not happen at all. These computers are known as your car’s engine control module (ECM) and for a good reason. They relay how fast your car is moving, how much oxygen it’s burning, and any other data related to helping your car run as efficiently as possible.
Whatever your problem may be, the diagnosis of the speedometer requires special tools. If you experience something wrong with your speedometer, the proper course of action would be to consult a mechanic that has all the tools necessary for a thorough tune-up and check-up ofyour vehicle.
Finding the Right Fit
If you have a faulty speedometer, and you’ve diagnosed it to be the direct problem, purchasing a replacement speedometer is the next step. To ensure that the replacement aftermarket speedometer will work properly and without hitch, purchase one that fits your car’s model year and make specifically. CarParts.com has search filters that help you narrow down your search in order for you to get the perfect fit in one try.
Tips on Buying a New Speedometer
Aside from the fuel gauge, the speedometer is probably the most frequently used instrument in your car's dashboard. After all, how will you know you're going 70 on a 55 mph lane? So once it stops working, it's imperative that it must be replaced.
Today, you can buy a speedometer gauge from any auto parts store, be it in the real world or in the web. And to help you find the right one, we've compiled some pointers for you to consider when shopping for a speedometer.
OEM or aftermarket?
If you are looking for a quick and easy replacement for your speedometer, OEM is the way to go. Original equipment manufacturer (OEM) speedometers are manufactured by the same company that made your car and are built to match its exact specifications. This guarantees that, barring any modifications on the dashboard on your end, the speedometer will fit perfectly on the dash and work just like the stock on in your car.
However, because they are built under strict guidelines, OEM speedometers tend to be bland and do not offer more in design and function. And if the latter is what you want, aftermarket speedometers may be right up your alley. Made by third-party manufacturers, aftermarket speedometers may require some tinkering in order to function properly in your vehicle but offer more customization and design options.
There are now aftermarket speedometers available that directly connect with your vehicle's OBD-II ports. This allows the speedometer to transmit other information about your car, such as battery voltage, coolant temperature, and other diagnostic information aside from speed. Some also have built-in warning indicators that light up whenever a vehicle encounters a specific failure in one of its components. These speedometers tend to be expensive, however, and only compatible with certain models. But if your vehicle supports speedometers with OBD-II functionality, we recommend giving these a try.
LED lights and displays
It is also recommended to buy a speedometer that uses LED lights instead of the traditional incandescent bulbs. While they do cost more, the LEDs used in speedometers can last tens of thousands of operating hours, so you're likely not to replace one due to wear. In addition, LED lights provide a much brighter hue, and its high degree of customization means you can have the speedometer light up in a variety in a variety of colors and patterns. These may not be compatible with some autos, however, to make sure to talk with your mechanic first whether you can stick an LED speedometer in your vehicle's instrument panel.
Speedometers normally rely on electronic pulses from speed sensors to determine speed, but there are also speedometers sold today that rely on GPS satellites. These GPS speedometers calculate speed, distance, and other information using satellites, allowing for a more precise reading. Also, since they do not require sensors in the vehicle to operate, GPS speedometers can be installed on any vehicle and require little or no calibration from the user.