The Peterbilt 379 is one of the most sought-after trucks manufactured by Peterbilt. It boasts many powerful features and is known for its durability. However, just like every piece of machinery, it also develops problems over time.
Many users have reported that the speedometer in the Peterbilt 379 truck stops working sometimes. Since this truck is designed mainly for highway use, the speedometer holds key importance as it allows you to keep an eye on the speed of the truck.
It shows you accurate traveling speed, allowing you to maintain a sensible pace. So, what causes the speedometer of the Peterbilt 379 truck to stop working? If you find yourself in a similar situation, this article is for you!
In this troubleshooting guide, we will take you through some of the common reasons for this problem, along with its common solutions to put a smile back on your face.
Peterbilt 379 Speedometer Not Working
Here are a few simple solutions to try if the speedometer of the Peterbilt 379 stops working.
1. Check Wirings
If the speedometer stops working, start by checking its wiring. A visual inspection is enough to detect the majority of the problems. First, make sure to turn off the Peterbilt 379 truck. Then, look for signs of damage on the wires.
If the wires are damaged, burnt, or have exposed ends, the speedometer won’t likely work properly. A large cluster can easily hide a damaged wire. If that’s the case, consider using your mobile flashlight.
However, a visual check may not be enough to spot a damaged wire in some cases. This is where a multimeter comes in handy. A multimeter is a device used to measure the electrical properties of an electric device or wire.
Nowadays, digital multimeters are also available on the market that measure the values more accurately while being compact.
Make sure to set your multimeter to 200 ohms before using it. Now, connect the wires to the multimeter. If it shows some reading, the circuit is complete. On the other hand, if you see an infinity sign on the display of the multimeter, it indicates that the circuit is open.
Simply replacing the wires will bring the speedometer of your Peterbilt 379 truck back to life. With little DIY skills, you can do it at home without needing any professional assistance.
However, if you do not have enough knowledge, refrain from handling the wires. Consider reaching out to a trained mechanic, and they will take care of everything.
In addition to that, be sure that the instrument cluster of your Peterbilt 379 truck is in good health. An instrument cluster is a board having a set of gauges, including the speedometer.
Sometimes, the problem is not with the speedometer but with the cluster. You can use a voltmeter to validate the integrity of the instrument cluster. If it has power, consider taking a closer look.
It is important to note that if the instrument cluster is defective, the other gauges on the board, such as the fuel gauge, will also stop working.
An instrument cluster has lines that carry the current from one point to another. If they have gone bad, they won’t be able to carry the current, and as a result, the speedometer of your Peterbilt 379 truck will stop working.
Carry out a visual check to see if the traces have burnt. If so, you will need a soldering iron and a few other tools to fix it. If you do not have these tools at home, it would be better to call in an expert.
2. Defective Speed Sensor
A malfunctioning speed sensor can also stop the speedometer of your Peterbilt 379 truck. A speed sensor produces signals that move the needle on the speedometer.
So, if there is something wrong with the speed sensor, the system won’t receive any data to measure the speed.
To check the speed sensor, you will have to locate it first. If you are unsure about its location, consider going through the user manual. The manual will help you locate it. Moreover, it will also have instructions regarding its replacement process.
Once you have located the speed sensor, check its condition. If it is broken, replacing it will be the only solution. The good news for you is that these sensors are readily available all over the world. Visit your nearby hardware store, and you will likely find one there.
3. Faulty Engine Control Unit
A failing engine control unit can also lead to this problem in the Peterbilt 379 truck. An engine control unit is often called the heart of the engine management system, and for a good reason.
It monitors various aspects of your vehicle, such as ignition timing, air/fuel mixture, and even speed. So, if this unit goes bad, your truck may not be able to recognize its traveling speed and will stay at zero most of the time.
If the engine does not start properly or dies soon after starting, the engine control unit may be the culprit. Furthermore, check to see if the unit is overheating. If it is, there is definitely something wrong with it.
The engine control unit is an expensive and complicated component, so replacing it requires skills and experience. If you lack these skills, it would be better to limit yourself to visual inspection.
Contact a mechanic and let them diagnose the problem. Once you have got it replaced, start your vehicle and see whether it has fixed the problem or not.
4. Blown-Out Fuse
The speedometer of the Peterbilt 379 truck comes with a fuse that protects it in case of power surges. It blows up to break the circuit when too much current flows through it, causing this problem.
Therefore, take a look at the fuse, and if it has blown out, replace it to resolve this issue. A voltmeter can also be used to determine whether it is working fine or not.
5. Replace the Speedometer
If you have tried all the solutions and the problem still persists, there is a high likelihood that you are dealing with a faulty speedometer. Be mindful that it must be installed properly, or else you may face the same problem even after getting a replacement.
And yes, you can contact Peterbilt customer support if the warranty hasn’t expired. This way, you can get a replacement while paying the least out of your pocket.
The Bottom Line
There have been many complaints regarding the speedometer of the Peterbilt 379 truck. From a faulty speed sensor to damaged wires, there could be many reasons why the speedometer may stop working sometimes.
We have mentioned several tried and tested fixes in this article that you can try if you face this problem.
