How to Troubleshoot the Battery
and Charging System of Your MarCum

When electronic units won’t charge, it can be frustrating for any angler. From batteries to chargers, to the system itself, it can seem confusing to determine what went wrong with your electronics and how to fix it. That’s why we have put together this quick battery troubleshooting guide. We break down each part of the charging system and step you through how to identify the problem and replace the parts if needed.

Understand Your Charging System

MarCum Charging System

The first step to successfully troubleshooting your battery is to first understand the charging system. There are 3 main components to the system. These are:

  • The Battery
  • The Wiring Harness
  • The Wall Charger

All three of these components need to be working properly for the unit to properly charge.


Most batteries are 12V SLA (sealed, lead-acid) batteries. They are commonly found in 12, 9, and 8 amps with our units. Many times, when batteries get old or damaged, they won’t hold a charge. Over-draining these batteries can accelerate this process. At this point, they will need to be replaced. You can purchase these batteries at

Battery Troubleshooting: SLA Battery

Wiring Harness

Battery Troubleshooting: Wiring Harness

Next is the wiring harness. This is a universal wiring harness with an SAE plug (male and female plug on one end). The other end has spade terminals to connect to the battery. In the middle, we have a removable in-line fuse. If it’s blown, the metal strip in the fuse will be cracked. Sometimes the wires on the harness can break or crack as well. In either case, it will need to be replaced. You can find a replacement on

Wall Charger

Next is a universal charger with and SEA plug. This will connect from the wall to your wiring harness. It is equipped with a light that changes from red to green when your battery is fully (and properly charged). This too can be found on our website.

Troubleshoot Your Battery: Wall Charger

Troubleshooting The Power System

Check The Battery

If you suspect the battery is damaged, check it with a voltmeter. All MarCum systems run on 12V and therefore should be reading 12.6 on your meter. If it reads too low, you should consider replacing the battery.

Check Your Wiring Harness

You can use a voltmeter to check the wiring harness. If there is no charge at the end of your wiring harness – your inline fuse is likely blown. You can replace that with any 2 or 3 amp automotive fuse. If you are getting voltage it means it’s working perfectly.

Wall Charger

If your wall charger isn’t working you will need to replace it. However, the wall charger can also signal other problems in the system. We go through each of these below.

The Charger Appears Green

The battery charging system is working correctly, the battery is charged.

The Charger Appears Red

The system needs to be charged.

The Charger Stays Red After 24 Hours

If the charger doesn’t appear green after 24 hours the battery likely won’t hold a charge. At this point, you will need to check it with a voltmeter. If it reads less than 12.6 volts it will need to be replaced.

The Charger Never Turns Red

In the case, where the battery needs to be charged, the charger still might not show red. This will likely mean you will need to replace the fuse.

The Charger Shows A Blinking Light

If you see a blinking light on the charger, then it likely means that the battery won’t take a charge. You will need to replace the battery.

We Have Everything You Need To Fix Your Battery Problems

We make replacing parts easy. Whether you need replacement batteries, wire harnesses, or chargers, we have you covered. Simply visit the replacement section of our found on our website to find any of these components, and we will have them shipped directly to your doorstep. This is just one more reason why troubleshooting your electronics is a breeze with MarCum.

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