How to Troubleshoot a Back Wall Infrared Heater Panel

The back wall of your sauna contains two or three infrared (FIR) panels, depending on your model. If one stops heating, you’ll notice a cold spot when doing a touch test on the back wall fabric from inside the sauna. This guide walks you through confirming the issue and identifying the faulty panel.

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 a Panel Isn’t Heating

After the sauna has been running for 5 minutes, press the back of your hand against the black fabric on the back wall above the bench. A working FIR panel will be noticeably warm to the touch. If you feel a section that’s cooler than the rest, there’s likely an issue with the panel sitting behind it.

Step 2: Check Connections First

Before opening anything up, rule out a loose power connection — these are the most common cause of a non-heating panel:

• Roof connections: Using a ladder, locate the C13/C14 power connectors at the roof and press each one firmly into place.
• 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 you still have a cold section after another heat cycle, move on to Step 3.

Step 3: Identify the Faulty Panel

The back wall FIR panels are accessed from outside through the slanted back wall. This step lets you check the wiring connections and, if needed, run a targeted test to pinpoint exactly which panel has failed.

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

1. Remove the back panel. Unclip all buckle fasteners on the latching back cover and set it aside.
2. Remove the back wood cover. Using a Phillips screwdriver, remove the screws securing the wood cover on the back of the slanted back wall. Set it aside — you’ll reuse the screws.
3. Check all connectors. With the cover off, you can see the back wall FIR panels and their wiring. Press each connector firmly to confirm it’s fully seated. If any were loose, reconnect them and run a heat cycle to test before going any further.
4. Run a targeted heat test. If all connectors were already secure, you’ll need to identify which panel has failed. Plug the sauna back in and run a 5-minute heat cycle. Then, from inside the sauna, press the back of your hand against the black fabric in front of each panel zone. The panel behind any cool section is the one that needs replacing. Once you’ve identified it, unplug the sauna.
5. Contact Plunge Support. Reach out to arrange a replacement panel before continuing. Having the right part on hand before you proceed will make the rest of this straightforward.