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Ask The Experts: How to Fix a Gas Gauge

Ask The Experts: How to Fix a Gas Gauge

You depend on your vehicle’s gauge cluster to keep you informed about everything going on while you drive. Gauges like the speedometer, tachometer, temperature gauge and fuel gauge all play an important part in driving. While some might argue over which gauge is the most important, a broken gas gauge is never good. 

Guessing how much fuel is in your gas tank may work for a little while, but odds are you will eventually slip up and run the gas tank dry. If you are trying to determine why your gas gauge does not work, the NAPA experts have you covered. Let’s take a look at how to fix gas gauge problems that might plague your car, truck or SUV.

How Do I Know If My Gas Gauge Is Bad?

If you just filled up your gas tank, and the fuel gauge needle is still sitting on “Empty,” then something is obviously wrong. If your car dies while the gas gauge tells you there is still plenty of fuel in the tank, then you have a little more detective work. One simple test is to reach under the vehicle and gently tap on the bottom of the gas tank. If it sounds like a hollow drum, then the tank is probably empty. But, if you are met with a thud or sloshing sound, then the problem lies somewhere else. 

You may also notice the gauge reading erratically fluctuating while driving, telling you a different fuel level every time you check. If you don’t feel like you can trust it anymore, then it is time to learn how to fix a gas gauge.

Inspect The Fuse

Start with the easy things. Without power to the gas gauge circuit, you will likely see an empty gas gauge. Check your vehicle owner’s manual for the instrument panel fuse location. Locate the vehicle fuse box, find the corresponding instrument panel fuse and remove it. Visually inspect the fuse for a break. You may also check the fuse for continuity with a multimeter just to make sure. If the fuse is intact, then it is time to move on to the next potential culprit.

Examine The Gas Gauge Senderfuel sending unit

Inside the fuel tank is a mechanical device called a sending unit. When you have a gas gauge not working, it is typically a problem with the sending unit. The sending unit uses a brass or plastic float attached to a sensor to measure the depth of the fuel inside the tank. Decades ago, the fuel sender was directly wired to the gas gauge, but in today’s vehicles the fuel sending unit transmits its signal to an onboard computer to operate the gas gauge. 

Removing the sending unit from the fuel tank is sometimes as simple as removing the rear seat cushion to expose an access panel or as complex as dropping the entire gas tank. You will need to refer to a repair manual for your specific vehicle for the exact method for accessing the sending unit. Any time the gas tank is opened for service, it is important to work in a well-ventilated area. Gasoline fumes can travel unseen across floors and explode, so don’t work in any areas where there is a possible a pilot light or anything that generates sparks. Likewise, do not use any tools that can create a spark. 

Typically, you can remove the sending unit retaining ring using a small hammer along with a brass drift or wooden dowel, carefully rotating the ring so as to not damage it. Once the retaining ring is removed, the sending units should lift up and out of the gas tank. With the sending unit resting on a workbench, check that the float arm moves smoothly and that the float is still attached. Use a multimeter to read the resistance of the sending unit while moving the float arm through its range of motion. The resistance should change smoothly. If the resistance is not within the specifications found in your vehicle repair manual, the sending unit is bad and needs replaced. 

Check The Gas Gauge Itself

Not much can go wrong with a modern gas gauge. On many vehicles, the gauge cluster is usually a single circuit board, unlike decades ago where a fuel gauge might reside in a separate pod somewhere on the dash. However, it is still worthwhile to check all electrical connections to the gauge cluster. Even if a wire connection is not loose, it could still corrode. Remove the gauge cluster connections and inspect them for discoloration or corrosion. When in doubt, clean the connections.

Inspect The Gas Gauge Wiring

Now we are getting into the details. If the sending unit is good, and the connection to the gauge is good, then you may have a wiring issue. The wiring harness between the gas gauge and the gas tank usually has a few connections and several feet of wiring. Inspect the wiring first, looking for any areas where the harness is damaged. Check the sending unit ground, as it may become corroded as time passes. Sometimes you may find a broken wire that is rubbed through after years of driving (or even chewed on by rodents). You may also find a loose ground wire.

Next, it is time to check the wiring itself. You will need a multimeter and a wiring diagram specific for your vehicle. If you have one, a wiring probe is extremely handy. Read the wiring diagram to locate which wires connect to the gas gauge. Now, use the multimeter to check each wire for continuity. Do the same for each wire that connects to the fuel sending unit. This is a tedious task, so it is usually left for last, but diagnosing an issue correctly is worth the time.

How Much Does It Cost to Fix a Gas Gauge?

Gas gauge repair cost varies depending on what is wrong. If it is just a fuse, then an automotive service shop may only charge a diagnostic fee and the cost of a fuse, so less than $100. If the problem is the sending unit in the gas tank, then it could cost between $400 and $1,000, including parts and labor. In some vehicles, the fuel pump assembly is part of the sending unit, making the replacement cost even higher.

If you went through these steps and are still stumped about how to fix a broken gas gauge, or prefer to let someone else do the job, your local NAPA Auto Care is happy to help. Our ASE-trained technicians have the training, tools and experience needed to track down the cause of your gas gauge not working. At NAPA Auto Care, our work is covered by the NAPA Nationwide Peace of Mind Warranty for 24 months or 24,000 miles.

Photo courtesy of Unsplash.

Brian Medford View All

With an automotive writing career spanning over two decades, Brian has a passion for sharing the automotive lifestyle. An avid DIYer he can usually be found working on one of his many project cars. His current collection includes a 1969 Olds Delta 88 convertible, BMW E46 sedan, and a slant-6 powered 1975 Plymouth Duster.

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