On some versions of the support documentation, a primary "Fault 4" refers to corrupted memory, which may require a unit reconfiguration. Honeywell Support Portal Recommended Troubleshooting Check for Heat Sources:

), making it suitable for both arctic and desert conditions. For "hot" applications, the

) and Oxygen. It features technology, which is specifically designed for high-performance in hot and humid environments .

Built to withstand harsh industrial environments, the XNX XNX ensures reliable performance under tough conditions.

For external sensor errors (like the Optima Plus), verify the white, blue, and orange wires are securely connected to the TB2 terminals exact wiring diagram for your specific sensor type (EC, mV, or IR)? XNX: Warning and Fault Codes - Honeywell Support Portal