Fuel Gauge Reads Empty When Full- Why Does It Happen?
Imagine this, you just filled up your vehicle to the fullest to see a full tank on the dashboard. Yet, the fuel gauge still shows empty, and at this point, you are just disappointed.
There has to be something wrong with the fuel tank in your car. There are multiple reasons why you might come across a deceiving fuel gauge that reads empty when full. Therefore, keeping every wire free of rust and debris is important.
Nevertheless, to understand why you have a deceiving gauge, you need to know how the fuel gauge actually works. This will let you see the bigger picture here. So without any further ado, let’s dig in deep and solve this together.
How Does A Fuel Gauge Work?
Right above the fuel tank is where the sending unit is placed. The sending unit can be considered to be in charge of all the processes. It is connected to a metal arm linked to an artificial hand called a float.
What the float does is quite fascinating. You can think of it as a robotic hand that measures the fuel in your tank.
The sending unit is connected to a potentiometer which helps to measure the resistance. What’s fun to imagine is that the float sits rights above the fuel level on your tank. So if the fuel on your tank is ¼, then it will stay exactly in the ¼ position of the fuel tank.
As a result, when the tank empties, the float creates resistance. As it is connected to a potentiometer, it notifies your vehicle’s dashboard for low on fuel.
On the other side of the sending unit is the fuel gauge. Any changes felt by the float are transferred to the sending unit. The sending unit then sends the information through the sending wire and finally to the fuel gauge which is connected to your dashboard.
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Fuel Gauge Reads Empty When Full- What Are the Causes?
Now that you know how a fuel gauge works, you are ready to know why you are coming across this specific problem.
So why does the fuel gauge read empty when full? The most common reason for this is due to the float getting disconnected from the metal arm. This makes the system not be able to measure the fuel level, and thus, you still see an empty fuel gauge. Other factors include;
- Damaged sender wire
- Blown fuse
- A malfunctioning fuel gauge
Don’t worry, we won’t leave you limited to these pieces of information only. We will discuss this further so that you can identify the exact cause of this problem.
Let’s discuss the causes and their fixes separately.
Cause 1: Float Getting Disconnected From The Metal Arm
The first thing you should look into when you come across a wrong reading is whether the float is connected to the metal arm or not. As mentioned before, this is the most common reason.
There’s nothing you can do about it, and neither is it your fault in the first place. You are just unlucky. So once you come across the wrong-read fuel gauge problem, open the fuel tank and see if the parts are in place or not.
You may have to replace the entire arm unit for this. Re-attaching isn’t possible when it comes to float and metal arms. So buy a new one and simply connect it to the sender unit and insert it into the fuel tank.
Keep steadily pushing the arm till you hear a click when installing the new one. The click sound is produced when the arm is in the right place.
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Cause 2: Damaged Sender Wire
From the diagram above, you can tell how important the sender wire is. Even if the metal arm can estimate the amount of fuel left successfully, it’s useless. As the metal arm passes the information to the sender unit, the sender unit isn’t able to send it back to the dashboard where you can see it.
It’s because the sender wire is responsible for sending all the information received from the system to the gauge where the users can see.
The only fix here is to replace the sender wire. There’s nothing much you can do with a damaged wire. However, when you are changing the wires, don’t miss the opportunity to clean the system with a cleaner (Our Pick) so that they don’t rust and get easily damaged.
Here’s a video that will help you achieve a proper wiring system;
Cause 3: A Blown Fuse
There are many fuses installed on a shelf in your vehicle for different uses. The one you are looking for is the Instrument Cluster Fuse. The main purpose of this specific fuse is to power the dashboard. It includes different gauges, including the fuel gauge and the speedometer.
Without sufficient power, the gauges won’t function. As a result, you might come across a fuel gauge that isn’t functioning at all. This is where you confuse a fuel gauge that reads empty when full with a fuel gauge that isn’t even working. The gauge just needs power which cannot be provided due to the blown fuse.
Underneath the dashboard or behind a panel next to the driver’s side door is where you’ll find the fuse for the instrument cluster. The fix here is to replace it. You can do it with no prior experience as long as you can identify the cluster fuse. Here are the 3 easy steps;
- Take out the old fuse from the fuse-box
- Take a look to see if the fuse is actually broken or not
- If broken, then get a new fuse and insert it into the place where the blown fuse was located
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Cause 4: A Malfunctioning Fuel Gauge
Have you ever thought that the fuel gauge itself could be the problem? Yes, it’s possible that the fuel gauge might have gotten broken, and everything else is working fine. One of the symptoms of a malfunctioning fuel gauge is that the fuel gauge reads empty when full.
On the other hand, a bad fuel-sending unit is one of the primary reasons behind a malfunctioning fuel gauge. So it’s best to also keep an eye on the sending unit to know if it’s working perfectly or not.
Once you make sure that the fuse and the sender wire are working fine, remove the ground wire and clean it. We mentioned making sure the fuse and the sending wire were working fine. The fuel gauge would malfunction anyways.
Coming back to the faulty fuel gauge fix, you need to remove the earth wire. The sender unit is connected to three wires. You should be able to spot a black wire, and that’s the earth wire. Take it off, clean it out, and place it back in. If it still doesn’t work, then replace the gauge.
Frequently Asked Questions (FAQs)
Let’s wrap things up with a FAQ session.
What Are The Symptoms Of A Faulty Fuel Gauge?
The fuel gauge meter may fluctuate, stuck on full or stuck on empty. If you come across any of these three situations, you may have a faulty fuel gauge.
How Much Does It Cost To Fix A Fuel Gauge Problem?
Depending on the problem, it might cost you around $60-$250. The prices also vary among car models.
Can I Drive With a Fuel Gauge that Reads Empty When Full?
There are no hazards linked to a malfunctioning fuel gauge. As long as you are certain that you have enough fuel, you are good to go.
To conclude, understanding why the fuel gauge reads empty when full isn’t that complicated. Once you know how the fuel gauge works, you can solve the problems yourself. The rule of thumb would be to make sure the wires are working fine, and the cluster fuse is not blown.
Most importantly, if you come across the wrong reading problems, just check the metal arm first. If it’s connected to the float, then shoot for other places. Or else, this should be a priority fix.
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