Bunn Slush Machine MONTHLY FILTER CLEAN REQUIRED: Cleaning Reminder
MONTHLY FILTER CLEAN REQUIRED is a reminder, not a breakdown. The air filter or rear screen that feeds the refrigeration system is due for cleaning, and the machine keeps running. Clean the screen, then hold the Left Dot button on the Ultra NX, or the ULTRA button on the older ULTRA, for 3 seconds to clear it.
Low: an operator reminder; the machine keeps running.
- Code
- MONTHLY FILTER CLEAN REQUIRED
- Maker
- BUNN
- Equipment
- Slush & frozen drinks
- Applies to
- ULTRA-1 / ULTRA-2 frozen drink dispenser and Ultra NX frozen beverage dispenser
What does BUNN MONTHLY FILTER CLEAN REQUIRED mean?
The control on these Bunn dispensers keeps a simple count of time, and when a month has passed it reminds you that the rear air screen needs cleaning. It does not measure how dirty the screen is, so the message is a calendar prompt, and the machine does not slow down or stop because of it. The reason for the reminder is what follows if it is ignored. A screen full of dust and grease cuts airflow to the condenser, the refrigeration side runs hotter, and the machine moves up to the FILTER NEEDS CLEANING messages, and eventually a shutdown. After cleaning, the reminder has to be cleared by hand with a button hold, or it will keep showing. Many calls we get for this message are simply a screen that was cleaned but never reset.
Affected models and control systems
This page covers the Bunn ULTRA-1 and ULTRA-2 frozen drink dispensers and the Ultra NX frozen beverage dispenser. The reset button differs between the two, as the steps below show.
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
- MONTHLY FILTER CLEAN REQUIRED shows on the display
- The machine freezes and dispenses normally
- The message returns after cleaning if it was never reset
Possible causes
Listed in BUNN's documentation
- A month has passed since the rear air screen or filter was cleaned
- Dust and grease built up on the screen
- Too little clearance behind the machine for airflow
- The reminder was not cleared after the last cleaning
Other likely causes — what usually sits behind MONTHLY FILTER CLEAN REQUIRED on this control. A technician confirms which one it is before any part is replaced.
- A cleaning that was done on schedule but the reset hold was missed, so the reminder keeps showing
- A screen in a greasy spot near a grill where the monthly interval is already too long
- A button hold that was too short, since the control needs the full 3 seconds
Safe checks before calling for service
- Clean the rear screen or filter with soapy water or compressed air, as the owner's manual describes for the Ultra NX.
- On the Ultra NX, hold the Left Dot button for 3 seconds to clear the reminder.
- On the older ULTRA, hold the ULTRA button for 3 seconds to reset it.
- Keep the back of the machine clear for air. If the message returns right after a reset, note the date and call us.
How a technician diagnoses MONTHLY FILTER CLEAN REQUIRED
- Confirm the model and which reset button applies.
- Inspect the rear screen and the condenser behind it for dirt that cleaning missed.
- Confirm the reminder clears and stays clear after a reset.
- Check that the airflow path and fan are normal, so the screen is not the only protection.
- Condenser cleaning behind the screen means removing panels on a machine with live wiring.
- A reminder that comes back right after a correct reset points to a button or control problem that needs testing.
- Checking the airflow path and fan goes beyond the screen the operator can reach.
Technical reference
- Document
- ULTRA-1/ULTRA-2 Service & Repair Manual 41084.0000D, Troubleshooting p.19-21
- Maker documentation
- BUNN owner support
- Edition
- 41084.0000D 03/13 (copyright 2009 Bunn-O-Matic Corporation)
- Models / control
- ULTRA-1 / ULTRA-2 frozen drink dispenser and Ultra NX frozen beverage dispenser
- Section
- Troubleshooting flowcharts: Torque Sensor Error p. 19, Temperature Sensor Error p. 20, Clean Filter Messages p. 21
- 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.
Related BUNN slush & frozen drink error codes
Can I ignore MONTHLY FILTER CLEAN REQUIRED?
You can for a while, since the machine keeps running, but a dirty screen leads to the overheating messages.
I cleaned the screen and the message is still on. Why?
The reminder has to be reset by hand. Hold the Left Dot button on the Ultra NX, or the ULTRA button on the older machine, for 3 seconds.
Is this the same as FILTER NEEDS CLEANING?
No. This is a monthly prompt. FILTER NEEDS CLEANING means the machine is actually running hot.
Need help with BUNN MONTHLY FILTER CLEAN REQUIRED?
A technician confirms the cause on site and gives you the price in writing before any work starts.