How to Replace the Fan in a Battery Charger

The Schumacher SE-4020 is one of the most common older battery chargers you’ll find in the field, which means there are plenty of them still being repaired and put back to work.

One component that can cause problems on these chargers is the cooling fan. The original SE-4020 design uses a small 12-volt DC fan powered through a fan controller circuit board. When that system fails, replacing the fan itself isn’t always enough—the controller board can also be the culprit, and those boards can be extremely difficult to find.

In this walkthrough, Rick and Scott from PLP Battery Supply demonstrate a practical alternative: replacing the original DC fan with a same-size AC fan and connecting it directly to the charger’s AC circuit. The result is a simpler, more readily serviceable setup that turns the fan on whenever the charger is running.

Key Takeaways

• The original SE-4020 uses a small 12-volt DC cooling fan and a fan controller board. A failed fan controller can be difficult or impossible to replace because the original boards are no longer readily available.
• Replacing the DC fan with an AC fan provides a practical workaround. PLP Battery Supply’s 7011330 AC fan is the same size as the original fan and can be installed in the existing mounting location.
• The replacement fan connects directly to the charger’s AC circuit, so it runs whenever the charger is powered.
• The fan’s airflow direction is important and should be oriented toward the transformer. 
• With the appropriate parts and connections, this modification can be completed relatively quickly.

Why the Original Fan Can Be Difficult to Replace

The original fan in the SE-4020 is a small 12-volt DC fan, but it isn’t simply connected directly to the charger’s power. Instead, Schumacher powered the fan from the secondary side of the transformer through a small fan controller circuit board. That creates two potential failure points. 

Sometimes the fan itself fails, in which case replacing it with a 12-volt DC motor can solve the problem. But based on our experience working on these chargers, the controller board is also responsible for a significant number of fan failures.

Unfortunately, finding a replacement controller board can be extremely difficult. Rather than trying to track down an unavailable board, we have developed a practical workaround: replace the DC fan and its controller setup with an AC fan connected directly to the charger’s AC circuit.

Because the replacement fan is powered from the charger’s AC input, it comes on whenever the charger comes on. You can hear the fan running, providing a simple indication that the charger is powered and operating.

1. Remove the Original Fan and Controller

With the charger disconnected from power and ready for service, free up the wiring around the original fan. The existing wires are bundled together with zip ties, so those need to be removed or cut to provide access to the fan and controller wiring.

The fan is connected to the small controller board, which is in turn connected to the charger’s existing wiring. Disconnect the wiring from the board and remove the screws holding the original fan in place. It’s helpful to keep those screws, because they can be reused to mount the replacement fan in the same location.

Once the original fan is removed, the controller board and its associated wiring can be set aside. The goal is to eliminate that original DC fan-control arrangement and prepare the charger for the new AC fan.

2. Prepare Wiring for the New AC Fan

The replacement setup uses the existing AC circuit rather than the original DC fan-control circuit. To make the connections, prepare the wires by stripping back the insulation and using piggyback terminals to connect the replacement fan into the charger’s existing AC wiring. The piggyback terminals provide a convenient way to make the new connections while retaining the existing wiring connections.

After preparing the wires and crimping the appropriate connections, the replacement fan is ready to install. For this repair, we use the PLP Battery 7011330 AC fan replacement. The replacement fan is the same size as the original, allowing it to fit into the existing fan location without requiring a different mounting arrangement.

3. Install the Replacement AC Fan

Before mounting the new fan, pay attention to the airflow and blade-rotation arrows marked on the fan housing. In this example, the arrow indicating airflow should point toward the transformer.

The orientation is important because the fan is being used to provide cooling airflow through the charger. Once the fan is positioned correctly, it can be placed in the same location as the original fan and secured using the existing mounting holes and screws.

4. Connect the Fan to the AC Circuit

The replacement fan needs two AC connections. In the walkthrough, we connect one wire to the timer, and the other to the input side of the switch. These connections allow the fan to receive AC power whenever the charger is turned on.

Once those two connections are made, the new fan no longer depends on the original 12-volt DC fan controller. Instead, it is powered directly from the charger's AC circuit.

It’s important to make sure the wiring is supported and secured rather than left loose inside the charger. After making the connections, the wires can be positioned so they are supported and kept clear of components that could interfere with them.

5. Testing the New Fan

With the wiring complete, the final step is to turn on the charger's timer and verify that the fan powers on. In our walkthrough, the fan starts immediately, confirming that the new AC fan is receiving power. Because the fan is now connected to the charger's AC circuit, it will run whenever the charger is operating.

The finished modification eliminates the original DC fan controller from the equation and provides a straightforward replacement for a system that can otherwise be difficult to repair when the controller board fails.

A Practical Solution for Older SE-4020 Chargers

The Schumacher SE-4020 has been around for a long time, and there are still plenty of these chargers in use. Practical repair solutions are especially valuable when original replacement components are no longer readily available.

Replacing the original 12-volt DC fan and controller with an AC fan helps extend the useful life of these chargers. The modification is relatively quick, uses a readily available replacement fan, and eliminates the hard-to-find controller board as a potential point of failure.

If you're battling with a non-functioning SE-4020 charger and aren't sure whether the fan, controller, or another component is causing the problem, PLP Battery Supply can help you identify the appropriate replacement parts and determine the best way to get your charger back in service.

Visit PLP Battery Supply to order the 7011330 replacement fan for Schumacher SE-4020 today. Contact our team at team@plpbattery.com or 800-642-3451 with questions about your charger or replacement parts.