Fish Finder Not Turning On: Troubleshooting Tips for When Your Fish Finder Won’t Turn On

Fish Finder Guides

There are several reasons why a fish finder may not turn on. Some of the most common issues include a dead battery, loose connections, a damaged power cord, a faulty circuit board, or other hardware or software problems. It is important to properly diagnose the issue before attempting to fix it, as many problems with fish finders can be easily resolved with a few simple steps. 

Reasons for Fish Finder Not Turning On

Angler using the fish finder on boat. Touching the screen and pointing at the sonar

Dead Battery 

A fish finder that won’t turn on could be due to a dead battery. This is a common issue, especially if the fish finder battery has not been used for an extended period. If the battery is dead, it will not provide enough power to turn the fish finder on.

Loose Connections

Loose connections can also prevent a fish finder from turning on. This can occur if the battery connections or the connections to the device itself are loose or not properly connected.

Damaged Power Cord

A damaged power cord can also prevent a fish finder from turning on. The power cord may be frayed or cut, which can prevent it from delivering the necessary power to turn the device on.

Faulty Circuit Board

A faulty circuit board can cause a fish finder to not turn on. This can be due to a manufacturing defect, corrosion, or physical damage. If the circuit board is faulty, it may need to be repaired or replaced.

Other Hardware or Software Issues

There may be other hardware or software issues that prevent a fish finder from turning on. For example, the device may have been dropped, exposed to moisture, or exposed to extreme temperatures, which can cause damage and prevent it from functioning properly. It is also possible for software issues to cause the fish finder to not turn on, such as if the software has become corrupted or the device has a firmware issue.

Troubleshooting Fish Finder not turning on

Check The Connection

fish finder connections at the back

Go to the back of your unit and ensure the power plug is fully inserted. It might help to unplug it and plug it back in. A simple restart should be your first step.

Try this step with each connection point of the wires going to your fish finder. It could just be a case of the plug slipping out a little, which may result in problems with the device turning on.

Battery Level

Fish finders usually require 12 volts for full power. If your battery level has dropped to below 12 volts, the fish finder might not turn on because of an insufficient charge.

  1. Confirm the Battery is Fully Charged: If the portable battery is not fully charged, it may not provide enough power to turn the fish finder on. The user should check the battery charge level and charge the battery fully if necessary.
  2. Inspect the Battery Connections: If the battery is not working properly, the user should inspect the battery connections for any visible damage or loose connections. The connections should be cleaned and tightened if necessary to ensure a secure connection.
  3. Try a Different Battery: If the battery still will not provide enough power to turn the fish finder on, the user should try a different battery to determine if the issue is with the battery or the fish finder.

Check the Power Cord

fish finder plug power cord

Inspect for Visible Damage: If the power cord is frayed or cut, it may need to be replaced in order to turn the fish finder on. You should inspect the power cord for any visible damage and replace it if necessary.

Test the Power Cord with a Multimeter: You can also test the power cord with a multimeter to see if it is providing the correct voltage. Consult the manufacturer’s manual for instructions on how to use a multimeter to test the power cord, as well as for the correct voltage readings for their particular fish finder. If the power cord is not providing the correct voltage, it may need to be replaced.

Blown Fuses

Another issue that can cause problems with your fish finder not turning on is any fuses connected to it. These could be on the device itself. They could also be wires attached to the battery or fuse panel.

Loose Or Bad Wiring

Wires and their connectors are other areas to check. If you have a poor crimp connection or a frayed wire, it might cause your fish finder not to turn on. Follow all wires going to your fish finder. If areas are sealed with a crimp or other connector, consider replacing that connection point.

Test The Unit

If possible, take your fish finder unit to another boat or battery setup. Test it on the wiring of that separate boat or directly to the battery. If the fish finder works, then the issue is related to the power supply in your boat. It could be the battery, fuses, or wiring.


In conclusion, if a fish finder is not turning on, there are several troubleshooting steps that can be taken to resolve the issue. These include checking the battery, connections and checking the power cord for visible damage and proper voltage readings.

Regular maintenance can prevent many issues from occurring with a fish finder. This includes cleaning the device and connections, inspecting the power cord for visible damage, and storing the device properly when not in use.

When working with electronics, it is important to follow safety guidelines to avoid injury or damage to the device. This includes reading the manufacturer’s manual, avoiding exposure to moisture and extreme temperatures, and avoiding excessive physical shock to the device.

Here are the product manuals of Garmin, Humminbird, and Lowrance to further find about the settings of your fish finder.