If your unit will not turn off, turns itself off, will not turn on or returns to the start-up or loading screen continuously, you should first:
Check for Proper Voltage
Check for proper voltage to your depth sounder at the connection to the battery or at the fuse panel. This will ensure that you are getting the proper voltage to the fish finder. The operating voltage range is shown in your Operations Manual. But a general rule of thumb is that the unit will not operate properly below 10.8 volts. It is advisable to check the voltage with all of your electrical equipment running as well as with the main motor and/or trolling motor running at different speeds to insure proper voltage and amperage. This may show an over-voltage, under-voltage or electrical interference condition. If you have an over or under voltage condition, it may be due to an inadequate charging system on your boat. Have your boat's electrical system inspected by qualified personnel.
A wet cell 12 volt battery is considered to be 100% charged at 12.7 volts. This is 2.12 volts per cell. A battery is considered completely depleted at 10.5 volts. At 11.31 volts, a battery is only at 10% charge; at 11.58 volts it is at 20% charge; and at 30% charge it, is 11.75 volts.
Battery manufacturers do not recommend going lower than a 30% charge and consider continual discharges to 20% to cause damage to your battery. For additional information on batteries and charge states please see the following links:
Check the Connectors & Pins
Check the pins of all connectors, to make sure they have not been bent, broken off or pushed back into the connector plug. If any connector pins have been bent, you may try to straighten them with needle nose pliers. If any pins are broken, replace the entire accessory.
Note: There is a risk that while straightening a bent connector pin, it can break.
Check the Cables
Check all accessories and cables for nicks, cuts, or physical damage. Try to repair any nicks in the cable with electrical tape. If any cables have had the internal wires cut or separated, the entire accessory or cable should be replaced.
Try wiggling the cable leading into the connector of the power cord to show any intermittent connection. If the power cable is intermittent, replace it. On some fish finders, an intermittent power connection may cause the microprocessor to cease correct operation. This may make it impossible to turn the depth sounder off. If this is the case, return it to the Service Department.
Run the power direct to your cranking battery
By running direct to your cranking battery, with the proper gauge wire and proper sized inline fuse, this could identify a bad connection to the fuse panel.
Use this as a test
to determine if there could be any crimps, nicks, cuts or poor splices in your existing battery to panel run. If the unit works correctly, directly tied to the battery, we recommend that you look at your existing panel/buss, fuse and/or panel to battery wiring.
If the wire gauge is too small for amperage or power draw, this can also create an issue. For a 15-20' run of cable, we recommend 12-14 gauge, tinned copper stranded wire. Some models (ION, ONIX or HELIX 12) may require a 10 gauge, tinned copper stranded wire.
Check the Unit
If possible, test the unit on another boat with the same model number and accessories installed. If your unit functions properly on the other boat, you know the problem is in the installation, accessories or cables. Here is a printable troubleshooting guide.