Middleby Marshall Oven Message: Belt Off – Oven Not in Temperature

What does Middleby Marshall Belt off - Oven not in temperature mean?

A conveyor oven should not move product into a chamber that is not hot enough to bake it. The touch-screen controller on a PS640G or PS670G holds the belt off during a cold start and tells the operator why with the message Belt off - Oven not in temperature. The manual treats this as normal, not a problem. As the burner heats the chamber, the temperature on the screen rises, and once the oven reaches its operating temperature, the belt starts moving without anyone pressing anything. How long that takes depends on the oven and how cold it was when lit. A wait of several minutes is ordinary. The message becomes interesting only when the wait is longer than it used to be, or when the temperature stops rising altogether. That would point to heating that is slower than before or not working at all, and it is the point at which a technician should look. Until then, staff do not need to touch the oven, reset it or reach inside.

Affected models and control systems

This applies to Middleby Marshall PS640 and PS670 conveyor ovens with the touch-screen controller, such as the PS640G and PS670G. Other controller generations word their warm-up messages differently.

Code numbers and their meaning can change between control generations. We match the full model and control before acting on a code.

What you may notice

• Belt not moving after the oven is switched on
• Message on the screen while the chamber is still climbing
• Chamber temperature rising slowly toward setpoint

Possible causes

Listed in Middleby Marshall's documentation

• How long the oven takes to reach temperature
• Whether the oven is heating at all
• Signs that heating is slower than it used to be

Other likely causes — what usually sits behind Belt off - Oven not in temperature on this control. A technician confirms which one it is before any part is replaced.

• Oven lit from fully cold, which takes the longest warm-up
• Burner that lights but runs weak, so the climb stalls
• Gas supply pressure low at the start of a busy morning

Safe checks before calling for service

How a technician diagnoses Belt off - Oven not in temperature

1. Time a cold start from lighting to operating temperature.
2. Watch the burner flame and ignition sequence.
3. Check gas supply pressure at the oven.
4. Check the thermocouple reading against a reference thermometer.
5. Check the heat controls and blower airflow.
6. Repair only the part that the test shows.

How Belt off - Oven not in temperature differs from similar codes

This message is a normal warm-up status, unlike High Temp Error, which reports a thermocouple or controller problem.

Technical reference

Document

PS640G I&O Manual 60251 Rev J, screen alerts

Edition

P/N 60251 rev J, (c) 2023 Middleby Marshall Inc.

Models / control

Middleby Marshall PS640 / PS670 touch-screen controller (screen alert)

Section

Section 3 Operation - Quick Reference: Troubleshooting, Screen Alerts table, printed p. 28

Checked

October 2026

We use the maker's document to read the code and do not reproduce it. Always confirm the complete model and control before applying these steps.