If your sauna is cutting out mid-session but can still be powered back on afterward, there are two likely causes. Both are straightforward to check.

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.

Cause 1: Smoke Detector Triggered

Your sauna has a built-in smoke detector that will automatically shut the unit down if it activates. If the shutdown was accompanied by a brief alarm sound lasting a few seconds, this is almost certainly what happened.

⚠ Important: Before troubleshooting, always confirm there is no actual smoke, burning smell, or safety concern inside the sauna. Only proceed once you’re sure the environment is safe.

If the sauna checks out and there’s no real cause for alarm, a dust buildup around the smoke detector may be triggering it prematurely. Here’s what to do:

• Clean around the detector: Wipe down the smoke detector on the back left of the roof with a damp cloth. Dust accumulation on or around the sensor is the most common cause of false triggers.
• Clean the sauna regularly: Routine cleaning of the interior — particularly the roof area — helps prevent dust buildup from becoming an issue. See our Cleaning Guide for details.
• Check the detector connection: Ensure the smoke detector cable is firmly plugged into its port on the control box. A loose connection can also cause unexpected shutdowns.

Cause 2: Control Box Overheating (HH Error Code)

If the UI display is showing an HH error code at the time of shutdown, the control box is running too hot and triggered a thermal protection shutoff. This is typically a ventilation issue rather than a component failure.

• Check the vent cover: Confirm that the mesh vent cover on the roof topper above the control box is free of any obstruction. Anything blocking airflow will cause heat to build up inside the box.
• Check clearance: Make sure the sauna has adequate clearance above the roof as specified by Plunge Customer Service. The control box needs open space around it to vent heat effectively.

Note: For more detail on the HH code and control box ventilation, see the UI Error Codes guide.

If neither of the above resolves the issue and your sauna continues to shut off unexpectedly, contact Plunge Support — we’ll help you track down what’s going on.