How to Tell if Your Transducer is Bad: Fish Finder Tips

Having a fish finder on your boat can make each fishing trip much more successful. Being able to have an eye under the water can help you locate groups of …

Having a fish finder on your boat can make each fishing trip much more successful. Being able to have an eye under the water can help you locate groups of fish, underwater structures, terrain changes, and water depth so you know exactly where to drop your line in the water.

Unfortunately, a bad transducer that isn’t working properly can give incorrect results or display a black screen entirely. When having electronic equipment installed on your boat, it’s important that you understand the best way to maintain and troubleshoot potential transducer issues. 

How Does A Fish Finder Transducer Work?

A fish finder transducer is a somewhat complex piece of electronic equipment for your boat. It contains a piezoelectric element that converts both electronic and acoustic sonar pulses into a readable format on a small screen you can view from the deck of your boat.

Having a sonar on board is a great way to locate your next trophy catch in all water types. The sonar will send sound pulses into the water that echo off of structures, rocks, logs, groups of fish, and other items to return a surface reading of those objects back to the main unit. 

As this electrical energy returns to the transducer sensors, results are displayed on the screen in such a way that makes it easy for you to tell what you are looking at. Depending on the quality of your transducer, you may only be able to see general groups of fish, or could be able to see single fish and track them as they move in high detail on the display.

In addition to being able to locate fish and other underwater structures, a new transducer can tell you the depth of the water you are fishing in. It does this by measuring the amount of time it takes for sound waves to hit and object in the water and return to the transducer.

Knowing the depth of the water can help you determine the best fishing setup to use when you want swift and accurate bites from fish in the area.

Common Signs of Transducer Trouble

Incorrect Depth Reading

If you know the water should be around 30 feet, but your transducer is telling you it’s 5 feet, you can consider this one of the signs that something is wrong. Not having an accurate depth reading is commonly due to air bubbles or interference from other electronic devices on board.

Poor Depth and Detail Display

If you’re noticing a lot of distortion and poor visual results on your transducer, it is most likely due to turbulence in the water. Ensure your transducer has been installed in the right spot so that water turbulence from the engines and trolling motor don’t cause issues.

Black Screen

When you turn your fish finder on and are greeted with nothing but a black screen, you can safely assume you have a damaged transducer. This is normally caused by heavily corroded cords, damaged cords, or a poor cable connection causing interference or too low voltage.

How Do You Test A Transducer: Checklist

Is the Transducer Covered in Marine Growth?

There are many forms of marine life that can attach to the main unit and the underwater components of your transducer. The depth measurement signals are what will be affected the most, so if you are noticing faulty reading results, you may want to check your underwater components for marine growth.

Is the Transducer Affected By Cavitation?

If you’re noticing issues in any readings or seeing very poor images when searching for underwater contours, try turning off your trolling motors and main engine to see if it improves the results. If it does, turbulence in the water is causing the problems.

Are there air Bubbles Around the Transducer Mounting?

If you notice any issues with the results on how deep the water is, visual readings, or water temperature on your electronic finder, one of the easiest things to check first is the mounting location of the unit. Sometimes simply moving the location of the transducer and receiver can clear up the issues.

Are the Cables Connected Correctly?

A boat is constantly moving, bumping up and down on the waves, and occasionally thumping into the dock or hauling trailer. All of these vibrations can lead to the cords becoming loose on your electronic finder. Regularly check the connections and make sure everything is fully plugged into the right spot without wiggling or feeling loose. 

In addition to the hull vibrating and causing a transducer cable issue, corrosion can also be a problem especially if you do a lot of saltwater fishing. As salt from the water spray gets onto your electronics, it can find its way into connections and switches on board. If possible, try removing cords and cleaning them with a damp cloth and mild detergent to remove built up salt and corrosion.

Is the Transducer at the Correct Angle?

Since transducers use a narrow beam sonar pulse, having them point straight down gives the sensors a good view below the boat to measure depth, contours, and structures. If you’re noticing distorted image results or questionable contour readings, your transducer may not be installed at the suggested angle.

Is a Nearby Fish Finder Interfering With Your Unit?

While you can have multiple transducers on your boat, they will each need their own spot on the boat to prevent interference between the units. Be sure to check your transducers user manual and factory settings to see how far apart each should be installed to prevent issues between the main transducer and the other machine.

Can You Repair a Bad Transducer?

While there are several issues that can happen to a transducer over time to reduce the accuracy of its readings, fixing it can be relatively quick and simple in some cases.

  • Loose Cables. Checking your transducer cords once a month or so can go a long way in preventing loose connections. Take a few minutes at the start or end of the month to make sure all transducer cords are plugged or screwed in tightly.
  • Cable Damage. Damage to the transducer cords can cause reading issues as well as complete failure in your contour finder. When you are checking the connections of your transducers, also check for damage and swap the cords as needed.
  • Cable Corrosion. If fishing in saltwater, corrosion is a common issue you may have to deal with on transducers. Rinsing off your transducer components after leaving the water can help reduce the chance of corrosion. Heavily corroded connections can be cleaned with a damp cloth or replaced entirely.
  • Transducer Angle. When installed properly, your transducer should be pointing straight down from the boat. If the angle has shifted due to vibrating or bumping into a structure, you can adjust the angle manually to see if this improves your sonar readings.
  • Cavitation. Transducers that show excess amounts of distortion when the boat is moving, check to be sure it is installed in the right location. Single engine boats should have the transducer installed on the starboard side, while dual engine boats should have it installed between the engines.

Do Transducers Wear Out?

Best fish finder under 500 feature image boat red with fish finder
Regular cleaning can be one of the most simple ways to maintain your fish finders and prevent short circuits or petroleum residue buildup.

As with all electronics, a transducer can wear out over time. Regular use over a long period of time can lead to wear and tear on the internal components. Overheating can also cause problems in most transducers if they are used out of the water.

Vibrations can also lead to transducer issues over time. As the boat is moving, the engine can cause vibrating that will slowly but steadily rattle internal transducer components around. If manufacturing quality was low, these components can break free of their housing and cause a complete loss of the transducer.

How Can You Maintain Your Transducer In Good Condition?

Staying on top of regular cleaning can be one of the most simple ways to maintain your fish finders and prevent short circuits or petroleum residue buildup . Simply take a damp soft cloth to avoid scratching and clean the exterior surface of your transducers.

You can also disconnect the transducers and clean the cord connections with a slightly damp cloth. Ensure they are completely dry before plugging them back into any transducers. Other ways to keep your transducers properly maintained include:

  • Paint the Exterior. Using an antifouling paint is a good option to prevent algae and scum from growing on the surface of your transducer. This will also help prevent the corrosion mentioned earlier from saltwater.
  • Only Use in Water. Transducers contain piezoelectric crystals that can quickly overheat when used out of water. In order to protect the electronic unit and prevent overheating, it’s important that you only turn on the transducer when the boat is in the water.
  • Inspect Cables. Cables that are damaged, corroded, kinked or twisted can be the cause of random readout issues or low voltage on your transducer. Always be sure your cords are in good condition and replace faulty or damaged cords quickly to eliminate transducer issues.

Final Thoughts on How to Tell if Transducer is Bad

Being an electronic device surrounded by water, there are several ways this machine can go bad or suffer from interference. However, troubleshooting the problem signs is often easier than you may think. Once you know what the issue is, you can quickly repair or replace the troublesome component and get back to having a properly working transducer to give you accurate signals from the frequency pulses.

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Jeff Knapp is an expert fisherman, guide and outdoor writer whose work is widely published across a range of sites including Tackle Village. Jeff is based in Pennsylvania and loves exploring the waterways of that state in pursuit of smallmouth bass, largemouth, panfish and trout.
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