Question: Gas Gauge Goes Up and Down While Driving: 6 Common Reasons

A functional gas gauge helps you know the amount of fuel in the tank and when to gas up. It’s a useful instrument you should regularly check, especially during long-distance driving. However, like most components in your vehicle, the gas gauge can act up and become unreliable.

Some drivers claim that the gas gauge goes up and down while driving, and they can’t figure out the cause. Often, you’ll see an erratic gas gauge if the vehicle has a defective fuel sending unit, wiring problems, a faulty gas gauge, a bad fuse, or old gasoline. 

Below we’ll discuss the reasons for a gas gauge behaving erratically. More importantly, you’ll learn how to address each issue to continue getting accurate readings.

Question: Why Does My Gas Gauge Goes Up and Down While Driving?

Your fuel gauge misbehaves when a loose float arm causes the float to move abnormally. The car’s float arm misbehaves either due to corrosion or wear and tear, affecting how the sending unit relays signals to the fuel gauge. I would recommend installing a new floater to resolve this issue.

Defective Fuel Sending Unit

The fuel-sending unit, also called the fuel gauge sender, resides in the gas tank. As its name suggests, this component sends signals to the gas gauge. It’s the one that allows you to know how much gas you have in the tank.

The fuel sending unit comprises float, arm, and resistor. There are situations when the float arm moves freely, causing the float to move erratically. This can happen when the float arm becomes loose, corroded, or worn out.

In this case, access the sending unit and assess it to see if the arm is loose or if the entire component is worn. If there’s corrosion on the metal arm, scrub the affected areas to remove it. A fuel system cleaner will help remove any stuck residue and corrosion.

Then ensure you have a tight arm as required. If the sending unit is not salvageable, find a professional to help install a new one.

Traversing uneven roads can cause the gas to slosh haphazardly, causing the float to have erratic movements. When this happens, the gas gauge will go up and down due to fluctuating signals. This issue is common in older models and stabilizes when you drive on even roads.

Most modern vehicles feature specialized subdivisions and baffles that prevent gasoline from sloshing while driving.  

Loose or Damaged Wiring

The connections and wiring on the fuel sending unit transmit signals to the gas gauge. Besides, the gas gauge and the instrument cluster have several wires and connectors for transmitting signals. Over time these wires and connections might become loose, corroded, worn, or damaged.

These issues can make the gas gauge bounce erratically. Use the manual to locate each wire and connector to examine them. Inspect these wires and connectors, paying attention to any defects.

You can disconnect the wires and examine the connection points. Clean these points with a contact cleaner spray if they look dirty or corroded. Wires can break or wear out and cause the gas gauge to misbehave. Replace them if necessary. Then connect them as tightly as possible.  

Sometimes, the wires and connectors might not show any wear or defect. If the gas gauge continues jumping up and down, connect a multimeter to the connectors and wires to check the resistance. Replace them if the resistance varies with what the manual indicates.

Faulty Gas Gauge

While it’s less likely for the gas gauge to fail, you can’t rule it out if it keeps changing irregularly. When the gas gauge goes up and down while driving, the possible culprit might be a bad internal circuit. The gas gauge might also have succumbed to damage if your vehicle had a recent accident.

If the gas gauge is to blame, you’ll see the needle jumping up and down or scanning at any level. Open the dash to remove the gas gauge. Your repair manual should provide steps for removing the gauge. Then use your multimeter to test the gauge’s voltage.

If the reading is below 12V or what the manual provides, replace the gas gauge. Physical damage to the gauge can cause this issue. Replace it if necessary. A DIY project will cost you between $50 and $200 to replace the gauge. The price will be higher – up to $500 – if done in the repair shop.

Instrument Cluster Failure

Modern cars have an instrument cluster on the dash. This instrument consists of LCD screens, buttons, and gauges. Since the gas gauge is part of the instrument cluster, failure of this system can cause the gauge to malfunction.

If the gauge behaves erratically, there might be issues with the instrument cluster. In most cases, defective circuits or physical damage are the possible causes.

To address the system cluster issues, use the manual’s instructions to pull apart the dash. Doing this should help you access the instrument cluster and test for low voltage. An experienced auto-electrician can help you diagnose and fix the problem.

Regrettably, repairing or replacing the instrument cluster is a costly fix. Depending on the repair shop, it might cost you from $700 to $900.

Bad Fuse

Every electrical component in your vehicle connects to a fuse in the fuse box. The fuse serves as a circuit breaker in the case of short circuits or over-current.

The gas gauge has a fuse in the box that can affect its performance. A blown fuse can affect the proper movement of the needle in the gas gauge. If the gauge goes up and down while driving, find the responsible fuse and fix it.

To do that, you must locate the fuse box first. Most vehicles have this box under the steering column, near the driver’s seat, or under the hood. No need for trials and errors, so use the manual to locate this box.

Open the fuse box and examine the gas gauge fuse. If you have a modern vehicle, you’ll find one fuse for the instrument cluster. The manual should come in handy when finding this fuse. Examine this fuse and replace it if blown. A fuse puller tool will help you remove the problematic fuse.

Old Gas

Allowing gasoline to sit in your vehicle’s tank will cause it to go bad over time. Regular gasoline will last from 3-6 months in the tank. On the other hand, diesel lasts twice as long, staying in good condition for around 6-12 months.

Gasoline left in the tank attracts air and moisture and creates bubbles. These bubbles multiply while driving and destabilize the fuel sending unit. As a result, the gas gauge will receive incorrect signals and fluctuate.

This will make it difficult to tell how much gasoline you have in the tank.

Drain the old gasoline and clean the tank, including the fuel lines. Old gas leaves residue under the tank and in the lines. After cleaning, refill the tank with fresh, high-quality gas. You can add a suitable fuel stabilizer to keep the gasoline fresh for a long time.

gas gauge goes up and down while driving

Final Thoughts

I have detailed why your gas gauge goes up and down while driving. Always ensure the gas gauge is functional to avoid disappointments while on road trips.

If the gauge malfunctions, the culprits could be the fuel sending unit, gas gauge, instrument cluster, fuse, gas, or wiring.

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