Fish Finder Doesn’t Work? Try Our Handy Troubleshooting Tips

Fish finder doesnt work feature image

A fish finder is an essential tool for anglers of all experience levels, as it can help you locate fish and underwater hiding spots. If your fish finder system won’t turn on the next time you hit the lake, it can be quite frustrating to figure out what the issue is or how to fix it. 

One of the most common reasons why a fish finder won’t turn on is power supply problems, but bad wiring, internal or external damage, and other causes may be to blame. This article will cover some of the possible causes and the best ways to diagnose and fix them.

Fish Finder Won’t Turn On – Power Supply Problems

Bad cables fish finder doesnt work
Fish finder systems may fail to turn on due to damaged cables or loose connections.

Bad Cables

One of the most common reasons why a fish finder system won’t turn on is due to bad cables. The cables may have been damaged during installation or transport, or there may be a loose connection between the cable connector and the fish finder itself.

Check the cables for any signs of wear and tear or any visible damage along the length of the cord or at the connector. Make sure that the cords are firmly connected to the power source and the fish finder transducer by gently tugging on them and pushing them in if loose.

If you find any damaged cables, you will need to replace them. If the cables are not damaged, but there is a loose connection, try unplugging and reconnecting the cables. You may need to clean the connectors in case some dirt or debris has gotten inside during a recent fishing trip.

Bad Wiring

Another possible reason why a fish finder system won’t turn on is because of bad wiring. Similar to a bad cable issue, the internal wiring may have become loose, or there may be a short circuit somewhere in the wiring. This can happen if the fish finder or depth finder is subjected to a lot of vibrations or extremely rough boating conditions or has been damaged from pulling on the cable or from a faulty cable when the unit was manufactured.

Inspect the wiring for any visible damage at the plug head or loose connections in general. Check if the wiring is properly connected to the power source and the fish finder. On some fish finders, you may need to check that the connector is installed in the right orientation. Some 4-pin plug connections can be installed upside-down, and while they will still connect, the unit won’t work correctly.

If you find any damaged wiring or bent pins in your connectors, you will need to replace the cord. If there is a loose connection, try unplugging and reconnecting both ends of the wiring. If there is a short circuit or you notice exposed wires around the base of the connector, you may need to seek the help of a professional.

Damaged Fish Finder

If the cords and wiring of your marine electronics are in good condition, the problem may be with the fish finder itself. The fish finder may have been damaged due to rough handling or exposure to moisture. While most marine electronics are normally water resistant, they may not be completely waterproof. Some external seals may be missing, or the unit could have been accidentally dropped into water.

Inspect the fish finder for any visible damage, cracks, or signs of moisture. In some cases, you may need to remove a few screws and open up the unit to look inside for signs of moisture or condensation.

If the fish finder is severely water damaged, you will most likely need to replace it. However, if the moisture is not too severe and hasn’t caused any corrosion on the internal components, try drying it out thoroughly before turning it on again.

Battery Terminals Corroded

Battery terminals corroded fish finder doesnt work
Check for signs of corrosion, like white or greenish deposits, on battery terminals, as it can cause fish finders to fail.

Another reason why a fish finder won’t turn on could be due to corroded battery terminals. Corrosion can prevent the battery from making proper contact with the terminals, which will prevent the fish finder from turning on.

Inspect the battery terminals for any signs of corrosion from saltwater or excess wear. Corrosion can be identified by the presence of a white or greenish deposit on the terminals. Try not to touch this with your bare hands since it can be irritating to your skin.

If the battery terminals are corroded, you will need to clean them thoroughly using a wire brush or sandpaper. You can also use a mixture of baking soda and water to remove the corrosion. Once the terminals are clean and a proper connection can be made between the power cable and battery, try turning on the fish finder again.

Sonar Image Interference: Transducer Problems

Transducer Cables Damaged

One of the most common causes of transducer problems is a damaged transducer cable. The cords may have been damaged due to normal wear and tear over time, could have been exposed to the elements, or damaged through rough handling.

Check the cords for any signs of damage or wear and tear. Look for any visible cracks, cuts, or frayed wires, especially at the end where the wire meets the connector. Slowly run your hand along the length of the unplugged cord to feel for damage to the exterior cover of the cables, which you may not be able to see.

If you find any damage on the cords, you will need to replace them. Make sure to use high-quality cables that are designed for use with your specific fish finder model to ensure the best connection and long-term reliability.

Transducer Badly Mounted

Another possible reason for sonar image interference is if a transducer is not mounted properly. If the transducer installation point is too far from a suitable spot, is too close to a trolling motor, or is angled poorly, it can cause the sonar signal to bounce off the hull of the boat resulting in a distorted or inaccurate image on the fish finder screen.

Check the mounting location and make sure it is suitable for your transducer. Ensure that the transducer is mounted according to the manufacturer’s instructions and that it is aligned correctly. 

If you aren’t sure about this, check the user manual that came with the transducer since it will normally have an installation guide. Make sure that it is positioned correctly and securely. After adjusting the placement, test the sonar image again to ensure that it is clear and accurate and that there is no sign of a weak signal or any voltage drops.

Transducer Picking up Interference

Sonar image interference can also be caused by a transducer that is picking up interference from other electrical equipment on the boat, such as radios or a depth sounder (a sonar device designed predominantly to get accurate depth readings).

Check the location of the transducer in comparison to any depth sounders or other electronic devices on the boat. Make sure that the transducer is not located near any other devices that could cause electrical interference.

If the transducer is picking up interference from a depth sounder or other device, you can try to reposition it or shield it using materials such as foam or rubber. You may also want to consider installing a narrow beam filter or choke to help reduce interference if you cannot move or do without the additional electronics.

Other Tips

Have the Latest Updates Installed

Fish finders and sonar devices may require firmware updates to fix bugs or improve performance. Make sure you have the latest updates installed on your device, or you may have problems with incorrect depth readings.

Restore Defaults

If you have made changes to the settings on your fish finder or sonar device and noticed issue afterward, you may want to try restoring the transducer or fish finder to its default factory settings to see if this resolves the issue and causes it to work properly.

Double Check Connections

Make sure all the connections between your fish finder or sonar device and the transducer are secure and properly tightened. Loose connections can cause interference or a loss of signal.

Check Fuses

If your fish finder or sonar device is not getting power or is experiencing other electrical issues, check the fuses on the boat itself. Replace any blown fuses with the correct type and rating.

Fish Finder Repair and Maintenance: FAQs

Garmin FIsh Finders Echomap Series

Will a Fish Finder Work Out of Water?

No, a fish finder will not work out of water. Fish finders use sonar technology to send and receive signals that bounce off of underwater objects, such as fish, rocks, and vegetation. When the transducer is out of the water, it cannot generate these sonar waves or receive any data making the device unable to function.

You may also have trouble with the fish finder if a large amount of air bubbles are allowed to gather around it. Air bubbles will prevent the sonar waves from bouncing off objects in the same way as they would if the fish finder was completely out of water.

Are Fish Finders Waterproof?

Most fish finders are designed to be waterproof to protect them from water damage. However, the level of waterproofing can vary between models and manufacturers. Some fish finders may be more water-resistant than others, so it’s important to check the specifications of your device and make sure it is rated for the environment in which you plan to use it.

How Can You Prevent Fish Finder Faults?

To prevent faults in your fish finder, you should follow these maintenance tips:

Regularly inspect the device for signs of damage or wear, and repair or replace any damaged components as soon as possible.
Clean the transducer regularly to prevent algae and other marine growth from affecting its performance.
Use high-quality cords and connections to ensure a stable signal and prevent interference.
Keep the device dry and protected from extreme temperatures and harsh weather conditions.
Follow the manufacturer’s instructions for installation, operation, and maintenance.
Keep the device up-to-date with the latest firmware updates to ensure optimal performance and bug fixes.

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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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