How to Tell if Your Fishfinder Transducer is Bad – Troubleshooting and Detecting Problems

Fish finders allow us to see everything below the surface of the water, so we know where fish are, what they’re chasing, and what depths they’re at.

While the digital display in your boat provides you with a picture of the underwater world, the eye in the water is the transducer.

A correctly functioning transducer is critical. 

Without it, you’ll get nothing but dodgy information on your display, if anything at all. Like any machine, transducers can break and malfunction.

Let’s troubleshoot some common transducer problems and some simple fixes.

How To Tell If Your Fish Finder Transducer is Bad? Troubleshooting

The first indication of a bad transducer is from the display. A number of things can go wrong, including poor images, depth readings that are incorrect, and variable performance caused by boat speed.

In some cases, you might not get any information at all, or you might get a few seconds of information and then nothing at all. 

Whatever the case, you need to try and isolate the problem. Sometimes it might be obvious, but often it’s a process of elimination.

How Do You Check and Test a Fishfinder Transducer?

We usually find issues with a transducer when we’re out on the water. This is generally the best place to test it.

You should avoid running your transducer dry because they can overheat and damage the internal crystals, resulting in shortened transducer life. 

Nevertheless, turning it on while it’s dry is fine for the 30 seconds you need to feel the pulse.

It’s pretty straightforward to figure out if the unit is getting power. Simply turn it on and feel it. You should feel the pulse, and you can hear it too.

With power going to the unit, you have eliminated connection issues. It pays to check your cables and connections for corrosion and excessive movement.

Sometimes connections fail intermittently due to a poor joint, connection, or corrosion. 

Boat movements can trigger or exacerbate this – one moment things are working fine, the next, there’s nothing.

Checking this is best done with another person. One person on the transducer, another on the cables making sure that movement is not causing a poor connection.

When you’ve established a good power supply, you need to check the readings on the screen.

This is best done at anchor in water where you’re certain of the depth and sea bed contour. 6 feet of clear water is great. 

You know the depth, and you can see the bottom.

Check the reading against your observations. If there are discrepancies, further investigation is required.

Again, knowing the basic contours of the seabed where you’re testing is handy. Motor steadily up to trolling speed and check the reading on the screen.

It’s a good idea to motor over a submerged structure such as a reef or deep hole that you’re familiar with or can actually see, to assess accuracy. 

Now you can test at different speeds.

If the reading is strong, consistent, and clean, as well as making sense relative to the depth, then happy days. 

If you’re getting a bad image, poor depth readings, or an inconsistent image, further investigation is required.

Checking the Positioning of the Transducer

A transducer should be positioned level with the bottom of the boat and facing directly down.

If it is not facing directly down (level with the boat bottom) then it will be projecting forward.

Depending on the severity angle, this can throw out depth readings significantly. The reading may also be blurry, or at least not to spec.

A transducer will not work properly unless it’s in clean water, IE, bubble-free. If it’s above the waterline, it will not work at all. Sonar does not travel through the air.

Bubbles are air and therefore will distort sonar readings. There are two main causes of bubbles, cavitation from the hull and propellers.

Positioning the transducer too close to the propeller, or at a place heavily impacted by cavitation, (often because of channels in the hull), will cause distortion.

Reposition the transducer as per manufacturers’ recommendations. 

Taking advice on this, particularly if it was installed in the wrong place to begin with, can be worth the time and fee – we don’t want a transom full of screw holes trying to get it right.

What Causes a Transducer to Go Bad?

What Causes a Transducer to Go Bad

More often than not, wear and tear, and poor cleaning are the top reasons we see transducers go bad.

There’s also leaving them running when they’re dry and other mishaps that tend to kill them.

While a transducer is, by and large, out of the way, they are still subject to the poundings from the water and the impacts when we strike buoys, logs, and branches.

When you think about the pounding your boat gets, they’re actually quite robust considering they’re such refined, precision tech.

Boat ramps, boat trailers, and mooring in the shallows or upon a beach are moments you need to remember that your transducer is at risk.

Be aware that if you’re running two transducers, interference can cause poor performance. 

Ensure they are placed far enough apart so as to not interfere with each other. Your owner’s manual should provide you with specific mounting details.

In many cases, an otherwise perfectly functional transducer will perform poorly due to some sort of impact.

Those transducers whose function has been tested a few times might require replacement due to age or malfunction.

Do Transducers Wear Out?

Over time, even the best-kept transducers will eventually wear out. Just like any other electromechanical device.

They see a lot of saltwater, UV rays, marine growth and endure plenty of impacts. 

The key component in your transducer is piezoelectric crystals. Over time, these crystals will degrade and eventually fail altogether.

Endurance can vary significantly and is entirely dependent on the life they lead. Cared for properly, they can last a long time.

Also Read: Can a Fish Finder Work Through Ice?

How to Keep Your Transducer in Good Condition

You can extend the life and ensure peak performance of a transducer simply by cleaning it. 

A damp cloth with soapy fresh water, used after every session on the water can work wonders.

Many paint their transducers with non-Ketone-based paints. While it adds protection, I’m more inclined to simply clean it.

Those whose boats are moored permanently in the water might find anti-fouling paint a good idea. 

Barnacles and corrosion work their devastating magic fast, and it’s best to prevent these issues from occurring as opposed to fixing them later.

Importantly, just don’t forget it’s there. It needs care and maintenance just like any other part of your boat.

You can’t find the fish without a working transducer!

And if you are interested in doing some ice fishing then you can take a look at our review of the best ice fishing sonars

Also Read: Can a Fishfinder Work Out Of Water?

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Sean Ward

Sean Ward

Hey there, my name is Sean – OnTrack Fishing is my site. I’m based in the UK yet I’ve been fortunate enough to catch bass in the States, barramundi in Australia, trout here at home and carp on the Danube delta. If I’m not fishing, or talking about fishing, then….I’m probably asleep.


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