When the display screen on an E+ shows ''XXXX'' it indicates that there is a fault with the sensor. In this instance the sensor must be replaced. Please view and order the replacement part online here: https://www.reznor.co.uk/product/e-thermistor/. Please refer to the E+ electric unit heater installation manual (https://www.reznor.co.uk/wp-content/uploads/2024/08/Reznor-e-Installation-Manual-EN-2024-06-D301600-Iss-0-print-quality-1.pdf) for more information.
What does it mean when my E+ display shows 'XXXX'?
Information on Reznor's range of warm air heaters