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Why Car Speedometer Not Working?

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Why Car Speedometer Not Working?

There might be nothing scarier than looking down at your vehicle’s dashboard and seeing that, though you’re driving, your speed is at “zero”. Not knowing how fast you are going puts you at risk of speeding tickets, not to mention it might make you feel out of control when driving. Car speedometers do sometimes break, and though unfortunate, you must immediately get ahead of the problem. 

A car speedometer not working might be due to something within your vehicle’s system that is broken or malfunctioning. You might have an issue with the wiring in your car, an engine problem, a broken instrument, or your speed sensor may have broken. 

Below, I will talk about the different possible things going on in your car that have caused your speedometer to stop working. I will also talk about some fixes for your speedometer, as well as a quick lesson on how your speedometer works. 

Reasons That Speedometers Stop Working

It’s dangerous to drive with a car speedometer that isn’t functioning correctly. It’s pretty apparent when the speedometer, or some remote part of it, is broken because your car will be moving yet still show a speed of zero. 

So what caused this problem? Your speedometer may have stopped working due to the following issues: 

  • Wiring issues
  • A broken speed sensor
  • Engine problems
  • A broken instrument
  • A blown fuse
  • A short in the wiring

If you can figure out what is going wrong in your vehicle, it’ll be much easier to fix the problem. 

Taking a shot in the dark and just picking one possible cause then fixing it will take a long time and may result in additional problems caused by user error. It’s crucial to figure out the exact reason your car’s speedometer isn’t working so you can move forward from there. 

Taking your vehicle to the dealer or a mechanic is the best way to do this, but understandably some of us may want to look for DIY fixes before risking a hefty bill from the mechanic. 

Read: Why Speedometer Is Not Working and Transmission Is Not Shifting?

How Your Speedometer Works?

Speedometers are standard in all vehicles, and though not as important as the engine or the tires, they might be the most relevant function in your car in a safe sense. Speed limits, as we know, are essential for keeping vehicles and drivers safe. Speedometers let us know when we are going too fast or too slow, both of which may put us in harm’s way.

There are two kinds of speedometers, which are mechanical and electric. 

  • Mechanical speedometers use magnetic currents. They use a rotating cable attached to the drive shaft, which is attached to a cable attached to the speedometer, to calculate how fast your vehicle is moving. 
  • An electrical speedometer, which is more common on modern vehicles, uses a speed sensor.

Though electric sensors are more common in modern cars, you still might find a mechanical one here or there. Regardless of what kind of speedometer you have, your speed will be displayed on the dashboard of your car via the following: 

  • Analog display: This is a display with numbers and an arrow that’s always there and moves up or down depending on your speed.
  • An electric display: This is a computerized screen that tells you how fast you are going. 

Read: TROUBLESHOOTING CAR’S ELECTRICAL SYSTEM

Wiring Issues

As mentioned above, your speedometer is a part of a complex set of wires that communicate to your dashboard in a few ways. Whether your car has an electrical or a mechanical speedometer system, the speedometer in your dash is usually connected via a cable wire to another part of your vehicle. 

When we go into our car to mess with the wires to fix something else or add a feature, we risk damaging some wires or not putting them back in the right place. 

This can cause your speedometer to stop working

Additionally, in the winter months, it can be common for critters to crawl under the dash or into the hood of your car. If they like to chew on wires, this can cause some vehicle problems, such as things not working correctly or wires getting exposed. 

Even if a rabbit or squirrel “only” exposed your wires, and didn’t eat them, having exposed wires can lead to water damage, which can ultimately stress your car’s system and cause some problems. 

Knowing whether or not it’s a wiring issue can be difficult. Still, you may consider getting suspicious about the wires in the dash if you were missing them recently or are having problems with squirrels or rabbits getting into your car.  

Read: Why Car Overheats?

Broken Speed Sensor

A speed sensor’s purpose is to send electrical pulses to your speedometer so that it can display how quickly you are driving. Your speed sensor, if you have an electric speedometer, usually plugs into your transmission. 

Even if you plug an electric diagnostic tool, a broken speed sensor might just stay on zero, even though you are moving. 

Read: Bad Speed Sensor Symptoms

Engine Problems & the ECU

Your Engine Control Unit commonly referred to as the ECU, is the computer that lives within your dashboard. 

Whether you have one of the “old-fashioned” (though its invention is still relatively new) speedometers that have a little red arrow that shoots up and up, or a computer version that tells you how fast you are going, you likely have an ECU in your car if it was made after 1981. 

Computer issues or communication problems between the ECU, the speedometer, or your dashboard can be detrimental to your car’s use. The ECU could be causing your speedometer problem if your speedometer isn’t working at all and remains on zero

If this is the case, you need to check out your ECU and see what’s causing the issue. It might be only a matter of time before other things in your ECU start getting wonky. 

Speedometer in Dash Broken

There is a chance that there’s nothing broken in the functioning of your speed sensors or cables, but rather your speedometer has completely broken. This would be most likely if you have an analog speedometer that just won’t move or if there are other things on your dashboard that haven’t been functioning correctly. 

This may have happened for a few reasons, like a blown fuse or an electrical issue. Worst case scenario, you’re looking at a broken or defective instrument cluster. 

Read: What Cars Have Best Autopilot?

How Do I Fix My Broken Speedometer?

Now that you’ve done some troubleshooting, you’ll need to know how to fix it. Is there a quick fix you can do right now, or is it something you need some more preparation for? Unfortunately, there are no quick fixes for this issue, and you can’t just turn your car off and turn it back on again, usually. 

You can fix your broken speedometer by troubleshooting the issue and proceeding from there. If you have a broken speed sensor in your electric speedometer, you can just buy a new part and replace it. Troubles with wiring, the ECU, fuses, or an instrument breaking might be a more complicated fix.

To scan for issues with your speed sensor versus your instrument, you can use a scanning tool or a diagnostic tool online or at an auto shop. These tools are pretty accessible and come with a range of different budgets. 

You can get a low-cost one like the MOTOPOWER Scanner Code Reader or opt for a fancier, more expensive one like the TOPDON AD500S Car Code Reader (both are available on Amazon.com). 

To use your diagnostic tool to see what’s going on, you can watch this video for a visual walkthrough as it pertains to your speed sensor and speedometer instrument:

Again, the fastest way to fix your speedometer might be just to bring it into a shop and have a mechanic take a look. 

Conclusion

If your car’s speedometer is broken, it’s essential to get the problem fixed as soon as possible. This can be a pretty low-cost fix when you go to a mechanic, and it might save you the time and stress of troubleshooting the issue just to go in and see what’s going on. 

However, if you want to do a DIY fix, you will start by checking for a few common problems. A car speedometer problem is usually caused by a wiring issue, broken speed sensor, ECU problem, or a broken instrument.

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