Temperature controllers
Watlow F4T Controller fault codes
What all 19 Watlow F4T Controller fault codes mean, in plain words, with a risk grade for each. These come from the manufacturer's own manual. The fix for each one is in WERCS Diagnose.
Get the fixes · plans from $49/moUpdated November 4, 2026
| Code | What it means | Risk |
|---|---|---|
| Low | Low The measured current has dropped below the low set point, causing the controller to halt the equipment. | GREEN |
| Fail | Fail The controller stops operating because a critical measurement failure has occurred within the system. | YELLOW |
| High | High The measured current has exceeded the high set point, which causes the controller to shut down the equipment. | GREEN |
| Open | Open The controller stops the heating process because a temperature sensor is broken or disconnected. | YELLOW |
| Error | Error The controller issues an error because a required file transfer did not complete successfully. | GREEN |
| Shorted | Shorted The controller stops the heating process because a temperature sensor has failed or shorted out. | YELLOW |
| Open Loop | Open Loop The process value has not responded to the loop outputs as expected, causing the controller to halt the operation. | YELLOW |
| RTD Error | RTD Error The controller stops the heating process because an error has occurred with the RTD temperature sensor. | YELLOW |
| Math Error | Math Error A controller calculation has no defined result, causing the system to halt its current process. | YELLOW |
| Stale Data | Stale Data Data from another controller is unavailable, causing the booth control system to lose communication. | GREEN |
| Not Sourced | Not Sourced The controller cannot process data because an input signal is missing or not connected to a function block. | YELLOW |
| Server Down | Server Down The controller loses network communication because the connection from the client to the server is missing. | GREEN |
| Need Host IP | Need Host IP The controller cannot connect to the network because the required IP address is missing. | GREEN |
| Ambient Error | Ambient Error The controller may fail because the surrounding ambient temperature is outside of its safe operating range. | YELLOW |
| Bad Calibration | Bad Calibration The controller will not function accurately because it has not been properly calibrated. | YELLOW |
| Reversed Sensor | Reversed Sensor The process value changed in the opposite direction than expected during heating or cooling, causing the system to stop. | YELLOW |
| Measurement Error | Measurement Error The controller cannot operate properly because an internal measurement error has occurred. | YELLOW |
| Need Host Name and IP | Need Host Name and IP The controller is missing a host name or IP address, which prevents network communication with the booth. | GREEN |
| Check Directory Permissions, Host Name and IP Address | Check Directory Permissions, Host Name and IP Address A file transfer failed due to directory or network issues, preventing the controller from updating its data. | GREEN |
Every code comes from the manufacturer's own manual. Subscribers see which manual and page.