Star Temperature / Thermocouple Error

What does Star Temperature / Thermocouple Error mean?

On Star UM-Series conveyor ovens, error codes appear as flashing text messages on the controller display for diagnostic purposes. A temperature or thermocouple error means the controller can no longer read a valid oven temperature signal. When this happens, the controller turns the temperature output off but leaves the conveyor belt running at the same speed so product is not trapped inside the oven.

Symptoms

• A flashing text error message on the controller display
• Temperature output shuts off while the conveyor keeps running
• Oven stops heating or will not reach the bake temperature setpoint
• Product exits the oven undercooked or pale

Common causes

• Open, shorted, or disconnected thermocouple
• Loose or damaged thermocouple wiring to the control board
• Thermocouple displaced from its mounting position in the oven
• Failed temperature controller or control board input

Diagnostic steps

1. 01

   Read the flashing message

   Note the flashing text shown on the display, since the controller reports temperature and thermocouple faults this way for diagnostic purposes.

2. 02

   Disconnect power before opening the control box

   Push the power switch to OFF and disconnect the oven from its power supply. Stacked ovens have more than one power connection point, so confirm all switches are off before servicing.

3. 03

   Inspect the thermocouple and its wiring

   Check that the thermocouple is seated in position and that its leads to the control board are intact and connected, with no pinched or broken wires.

4. 04

   Verify the heat output stays off

   Confirm that the controller has turned the temperature output off while the conveyor continues to run, which is the documented response to this error.

5. 05

   Call a service technician if it persists

   If the error remains after checking the thermocouple and wiring, contact your local service company, a factory representative, or Star Manufacturing.

When to call a professional

Clearing a temperature or thermocouple error requires opening the control box, where line voltage is present, and testing the thermocouple and control board. The manual warns that more than one power supply connection may exist on stacked ovens and that improper service can cause electrocution. If you are not trained to work inside the energized control box, or the flashing error returns after checking the thermocouple, contact your local service company, a factory representative, or Star Manufacturing.