Taylor Thermistor Probes: Hopper & Barrel Failures Explained
If your Taylor soft serve machine has a digital display and flashes HOPPER THERMISTOR FAIL or BARREL THERMISTOR FAIL on the screen, the issue is almost always a bad probe. In non-display machines, indication of a bad thermistor probe would be failure to maintain Standby mode barrel temperatures or temperture on both hoppers. These small temperature sensors play a big role in how your machine cools, freezes, and protects your product. Here’s what they do, why they fail, and how to fix the problem quickly.
What Does a Thermistor Probe Do?
Taylor machines use two types of thermistor probes:
-Hopper Probe – Monitors mix temperature in the hopper. Keeps mix below 41°F (5°C) for food safety. If temps go too high, the Softech display will lock the machine out.
-Barrel Probe – Monitors the freezing cylinder. Controls product viscosity and ensures the machine doesn’t over- or under-freeze the mix.
Both probes send continuous signals to the Softech control system. If a probe fails, you’ll see an error and some models will shut down to protect product safety.
Common Thermistor Failure Error Messages
When a probe fails, you’ll typically see one of these on the screen:
- HOPPER THERMISTOR FAIL
- BARREL THERMISTOR FAIL
Each of these can include a sub-message:
- SHRT → Probe shorted out.
- OPEN → Broken/disconnected probe.
- OVER → Over-temperature condition.
Why Thermistor Probes Fail
Even though probes are simple parts, they operate under harsh conditions:
- Freeze/thaw cycles – constant temperature swings wear out the sensor.
- Moisture intrusion – cracks in the seal let mix seep in.
- Wire fatigue – pinched or bent leads during cleaning and assembly.
- Electrical surges – sudden spikes can damage the sensor.
Signs You Need a New Probe
- Hopper won’t cool below 41°F (you may also see MIX TOO WARM).
- Product won’t maintain temperature in Standby mode.
- Random shutdowns with “THERMISTOR FAIL” messages.
- Barrel temperature readings don’t match actual product Temperature.
▶️ Not sure if your probe has failed? Watch this step-by-step guide on testing a thermistor probe with a multimeter Here.
Replacing Thermistor Probes
- No calibration: Probes cannot be adjusted or repaired. Once they drift or fail, they must be replaced.
- Replacement interval: Many operators change probes every 1–2 years as preventive maintenance, similar to tune-up kits.
- Easy swap: Hopper probes are quick plug-ins. Barrel probes require removing the front door and product to let the machine come up to room temperature.
▶️ Need to change a hopper or barrel Thermistor Probe. This video is a quick walk through. Watch Here.
Why Choose Partex / Soft Serve Parts Probes?
Partex-manufactured probes are:
- Precision-made to match factory specs within ±1°F.
- Durability-focused, with improved epoxy seals to keep moisture out.
- Made in the USA, ensuring consistent quality and availability.
- Cost-effective, with faster shipping and lower prices.
- Compatible with popular models like C712, C713, C723, 794, 336, 791, and more.
Final Thoughts
If your machine shows HOPPER THERMISTOR FAIL or BARREL THERMISTOR FAIL, replacing the probe is the only solution. A reliable probe protects your product, reduces downtime, and keeps your soft serve business running smoothly.
👉 Check out our full line of Taylor thermistor probes and tune-up kits to keep your machine in top condition.