Middleby Marshall Pizza Oven Alert Control Over Temp: Clogged Filters

What does Middleby Marshall Control Over Temp mean?

The controls of a conveyor oven sit in a compartment at the front, and they are kept cool by air drawn in through filters. On a PS640G or PS670G, the controller reads the temperature of that compartment. Control Over Temp means it has climbed too high, and the manual links this to the front filters being clogged. Dust, grease and flour build up on the filters, the air slows, and the compartment overheats. Because pizza kitchens are full of flour and grease, this happens often. The alert is the first warning in a pair: if the filters are left dirty, the next message is High Control Compartment Temperature, and after that the oven shuts down. Cleaning or replacing the filters usually clears the alert. If it keeps returning with clean filters, something else is heating the controls: the cooling fan may not be moving air, there may be no clearance around the oven, or the temperature sensing may be misreading. A technician can sort out which.

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 use different alert text.

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

• Control Over Temp on the touch screen
• Warm air at the front of the oven near the controls
• Filters coated in grease or flour

Possible causes

Listed in Middleby Marshall's documentation

• The front filters for dust, grease and flour buildup
• Airflow to the control compartment
• The control compartment cooling fan
• Controller temperature sensing

Other likely causes — what usually sits behind Control Over Temp on this control. A technician confirms which one it is before any part is replaced.

• Flour dust packed into the filter mesh after a long dough-heavy shift
• Oven pushed against a wall or cabinet, leaving no room for intake air
• Cooling fan slowing as its bearings wear

Safe checks before calling for service

How a technician diagnoses Control Over Temp

1. Read the alert and check filter condition.
2. Check clearance and room temperature around the oven.
3. Confirm the control compartment fan runs and moves air.
4. Check the compartment temperature sensing against a thermometer.
5. Look for other heat sources near the controls.
6. Replace the fan or sensor only after the test.

How Control Over Temp differs from similar codes

High Control Compartment Temperature is the stronger warning that follows this alert if the filters stay dirty.

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.