How To Tell If Your Fish Finder Transducer Is Working (& How To Troubleshoot Common Problems)


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?

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

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). 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 defect is coming from.

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 inspect 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. Read more about this in our articles on can a fish finder work out of water, and can a fish finder work through ice

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 test a fish finder transducer?

The first thing you can do to check 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.

Transducer losing bottom at speed

If there is a problem with the reading when the boat starts moving, this could be 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, which can impair transducer performance. 

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 need to get a professional to help you with this.

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. 


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.

If you’re planning to get a new fish finder, you may be interested in our reviews of the best fish finder under $200, and the best fish finder under $300. And if you’re into ice fishing, check out our review of the best ice fishing flashers.

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