How to Troubleshoot a Side Wall Infrared Heater Panel

The side wall infrared (FIR) panels are the primary heat source inside your sauna. If a panel stops working, you’ll usually notice one section of the sauna not reaching temperature, or a cold spot when you do a touch test on the wall fabric. Here’s how to diagnose the issue.

Please take photos or videos at each step of the troubleshooting process. If we need to order replacement parts, our Support team will use these to process your warranty claim.

Step 1: Confirm the Panel Isn’t Heating

After the sauna has been running for at least 5 minutes, press the back of your hand against the black fabric on the affected side wall above the bench. A working FIR panel will be noticeably warm to the touch within that timeframe. If the fabric feels cool, there’s likely an issue with that panel or its wiring.

Step 2: Check Connections First

Before pulling anything apart, check the most common cause of a non-heating panel — loose power connections:

• Roof connections: Using a ladder, locate the C13/C14 power connectors at the roof and press each one firmly into place to confirm they’re fully seated.
• Control box: On the AC bay of the control box, press each C14 plug in firmly to ensure none have worked loose.

If all connections are secure and the panel is still cold after another heat cycle, move on to Step 3.

Step 3: Check the Panel’s Internal Connector

There’s also a connector inside the wall where the FIR panel plugs into the sauna’s wiring. Checking this requires removing the back panel and accessing the side wall cavity, but it’s straightforward.

⚠ Important: Unplug the sauna from the wall before proceeding. Do not work inside the cavity with the sauna powered on.

1. Remove the back panel. Unclip the buckle fasteners on the latching back cover and set it aside.
2. Remove the FIR wood holder panel. Inside the back wall cavity, use a Phillips screwdriver to remove the screws securing the wood holder panel for the affected side wall FIR panel.
3. Expose the connector. Gently pull the wood panel outward, slowly, until the edge of the FIR panel becomes visible. There will be wiring connected to the bottom of the FIR panel — continue pulling gently until the connector emerges from the wall.
4. Check the connection. Confirm the connector is fully plugged in and seated. If it had worked loose, reconnect it firmly, reassemble, and run a heat cycle to test before continuing. If the connector was already secure, the panel itself is likely faulty and needs to be replaced — contact Plunge Support to arrange a replacement part before going further.