Bunn Slush Machine TORQUE SENSOR OPEN: No Signal from Sensor
TORQUE SENSOR OPEN means the control gets no signal from the sensor that tracks how hard the auger is working. The usual finds are an unplugged sensor or a broken wire. Note which barrel shows it, keep the lid in place, and leave the back of the machine closed until a technician looks.
Medium: the barrel cannot be managed without the torque signal and the machine may stop or over-freeze.
- Code
- TORQUE SENSOR OPEN
- Maker
- BUNN
- Equipment
- Slush & frozen drinks
- Applies to
- ULTRA-1 / ULTRA-2 frozen drink dispenser
What does BUNN TORQUE SENSOR OPEN mean?
Frozen drink thickness is controlled by how much effort the auger needs to turn through the product. The ULTRA-1 and ULTRA-2 measure that effort with a torque sensor, and the control uses it to decide when the product is frozen enough to stop. When the torque sensor circuit reads open, as if no sensor were connected, the control shows TORQUE SENSOR OPEN. With no torque signal it cannot manage thickness, and it may freeze too long, not long enough, or shut the barrel down to be safe. The causes the manual points to are on the wire side: a plug that has loosened, a wire that has broken or been chafed along the barrel, a sensor that has failed, or a dead sensor input on the board. None can be fixed with a reset. Because the machine is vibrating and being cleaned around daily, plugs and wiring at the barrel are the first places a technician looks.
Affected models and control systems
This page covers the older Bunn ULTRA-1 and ULTRA-2 frozen drink dispensers.
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
- TORQUE SENSOR OPEN shows on the display
- One barrel stops freezing or runs without shutting off
- Product comes out too soft or too hard
Possible causes
Listed in BUNN's documentation
- A torque sensor plug that has loosened at the control
- Sensor wiring broken or chafed along the barrel
- A torque sensor that has failed and sends no signal
- A dead sensor input on the control board
Other likely causes — what usually sits behind TORQUE SENSOR OPEN on this control. A technician confirms which one it is before any part is replaced.
- A wire that was flexed at the barrel each time the machine was pulled out for cleaning
- A sensor plug that vibration has worked partly out of its socket over months
- A sensor wet by a leak from the barrel seal that has reached the connector
Safe checks before calling for service
- Write down which barrel shows the message.
- Make sure the barrel still has product above the minimum fill line, and keep the lid in place.
- Do not unplug or open anything at the back of the machine.
- Leave the machine switched off if the message stays on, and call us with the barrel and what the product was doing.
How a technician diagnoses TORQUE SENSOR OPEN
- Read the display and confirm the barrel and the model.
- Inspect the torque sensor plug, wire and mounting for movement, breaks and moisture.
- Check continuity and resistance of the sensor and its wire with a meter.
- Check the control board input with the sensor disconnected.
- Replace the sensor, wire or board only after the readings show which one has failed.
- Without the torque signal the machine can over-freeze the barrel, which strains the auger drive.
- The sensor sits at the barrel and drive, so reaching it means opening the machine around moving parts and wiring.
- Finding a broken wire or a failed sensor takes a meter and the right replacement part.
How TORQUE SENSOR OPEN differs from similar codes
TORQUE SENSOR SHORTED is the matching message for an impossible reading. OPEN means no signal at all.
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
- 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 keep serving with TORQUE SENSOR OPEN on?
It is better not to. The control cannot judge thickness, so the barrel may over-freeze and strain the drive.
Will it clear by itself?
Rarely. If it does, a loose plug is likely, and it will probably return.
Is this the same as TEMPERATURE SENSOR OPEN?
No. This sensor measures auger effort, not barrel temperature, and adding product will not clear it.
Need help with BUNN TORQUE SENSOR OPEN?
A technician confirms the cause on site and gives you the price in writing before any work starts.