How To Tell If Your Fish Finder Transducer Is Bad (Problems & Fixes)


by Robert Ceran

Fish finders greatly improve your chances of catching fish, but unfortunately they don’t always work correctly.

If your fish finder isn’t performing as it should, one possibility you need to consider is that the transducer isn’t working properly.

So how can you tell if the transducer is bad?

How to tell if transducer is bad (fish finder troubleshooting)

Here’s the quick answer:

First of all, check the transducer for damage or dirt on its surface. If you find dirt or barnacles, clean it gently.

Next, check that it is positioned correctly, with the right orientation towards the bottom. Also check that the connection to the main unit is undamaged.

If all of this looks good, and you’re still not sure what is causing the problem, swap either the transducer or the main unit and test again, which should give you an unequivocal answer.

Troubleshooting a fish finder transducer

If your depth finder is not reading correctly, there are a number of different reasons that can cause a fish finder to perform incorrectly, so the first step is to get an idea where the problem is originating from.

Fish finders consist of two main parts: the transducer, and the display/processor unit (for more details, take a look at our article on how does a fish finder work).

If your display has a weak signal, or fails to turn on at all, it could also be due to a drained battery (in order to avoid that happening, check our review on the best fish finder battery).

One indication that the transducer is likely to be the cause of the problem is if you get an incorrect reading on your fish finder display. Here are the most common types of incorrect display readings that are caused by transducer errors:

  • Display shows surface reading, but no bottom reading
  • Display shows wrong depth reading
  • Display shows erratic readings (especially when the boat speeds up)

If you observe one of these issues on your fish finder, the next step is to examine your transducer for the following problems:

  • Is it installed correctly (as specified in the user manual)?
  • Is it correctly oriented? Most models need to be precisely oriented towards the bottom, and will not work properly if bent in a different direction.
  • Any signs of damage on the transducer?
  • Any barnacles or dirt on it?
  • Are the connector cables damaged?
  • Are you getting interference from several transducers with the same frequency close to each other?
  • Is cavitation affecting it (turbulence caused by the movement of the boat)?

If you find one of these problems, try to fix it if it’s something that can be easily alleviated, and then test again.

If you don’t see any of these issues, and you’re still not sure what part is causing the problem, then the best way to find out for sure is by testing a different main unit with the transducer, or by testing a different transducer with the main unit.

This will give you an unequivocal answer about which part is at fault.

Do transducers wear out?

Yes, absolutely. Transducers use piezoelectric crystals to send and receive sonar pulses, and these crystals can become cracked through wear and tear, which stops them from working properly.

The crystals can be damaged from physical shock (for example if you bump into something hard with your boat), which is unfortunately difficult to avoid entirely.

Years of abuse tend to add up, which causes transducer performance to degrade over time.

A transducer can also be damaged if it is run out of water. The reason for this is that the crystals overheat, which can also lead to cracking.

Especially CHIRP models overheat quickly, as their crystals send many pulses in a short amount of time, so make sure you never run them out of the water.

You can read more about CHIRP in our article on how to read CHIRP sonar.

Most transducers can last 10 years or more if maintained correctly. If your transducer is older than this, it may be the reason why your readings aren’t as good as they used to be.

How do you check a fish finder transducer?

The first thing you can do to test if your transducer is working is to turn it on and touch its surface. You should be able to feel the sound pulses as vibrations, and often you can also hear them as clicking sounds. 

Next, in order to test its performance, do this:

  1. Conduct the first test in water of medium depth, where you already have a good idea of the depth.
  2. The first test should be done without the boat moving.
  3. Turn on the display and check if it’s receiving a signal from the transducer.
  4. Check if there is a depth reading, and if it looks accurate.
  5. If all this looks good, you can then repeat it with the boat moving, slowly at first, and then faster.

Depth finder not reading correctly while moving

If there is a problem with your sonar reading when the boat starts moving, this could be due to the transducer losing bottom at speed, which is usually caused by cavitation.

Cavitation refers to water turbulence and air bubbles that are generated on some parts of the hull when the boat is moving, and this can interfere with transducer performance. When this occurs, it is usually caused by the fact that the transducer is mounted on a part of the boat hull where turbulence is too strong

If cavitation seems to be the problem, refer to the user manual for best practices on where & how to position it for better performance. You may also want to get a professional to help you with this.

Finally, transducer problems can also be caused by your trolling motor, via electric interference. In order to check for this, test your transducer with and without the trolling motor on.

How to maintain your transducer in good condition

Check your transducer periodically to make sure that it’s still oriented correctly. Transom mounts get bent out of shape quite easily over time, which impairs performance.

Also, check if there are barnacles or other marine life on the surface, which is a common issue if you’re fishing in saltwater or brackish water. If there are, scrape them off with a metal object, and then file down the remaining fragments.

A great way to avoid marine growth, or at least to slow them down, is to cover the transducer with antifouling paint. Make sure you use one that uses a water based solvent, as this won’t damage the surface.

If you can take it out of the water, regularly clean it gently with a soft cloth and mild detergent to keep the surface clean. Finally, you should also check the cables and connection elements for damage or corrosion. 

Closing remarks on how to tell if transducer is bad

I hope these tips will help you to troubleshoot your transducer, and to take good care of it so that it delivers optimal performance for many years.

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