Cissell 120/170 lb Dryer Error Code OP: Open Thermistor
OP reports an open thermistor: the temperature sensor circuit reads as broken or disconnected, so the control has no heat reading. The dryer stops, often with wet laundry still in the large drum. Switch it off at the disconnect, let the big drum cool, clean the lint screen and try one cycle.
Medium: the dryer stops until the sensor circuit is repaired, and the large drum holds the load.
What does Cissell error code OP mean?
A 120 or 170 lb Cissell with the micro control, such as the CT120N or CU120L, watches drum temperature through a thermistor. The control reads the sensor's resistance continuously. In the OP case that resistance is infinite, as if the circuit had been cut, and the control knows no real temperature looks like that. Without a real reading it cannot manage the burner or heater, so it stops and shows OP. The large drum holds a lot of laundry, so the first sign is often a heavy wet load that has to be moved to another machine. The manual lists a loose thermistor plug or corroded contacts, a broken wire along the sensor lead, lint packed around the thermistor and a failed sensor input on the micro control. On a dryer this size the sensor lead is longer and passes more panel edges, so a chafed wire is a common find. The drum cannot be reloaded until it cools.
Affected models and control systems
This page covers the Cissell 120 and 170 lb tumble dryers with the micro control, C-prefix models such as the CT120N and CU120L. The OPL control uses EoP for the same condition.
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
- OP appears and the dryer stops
- Wet laundry stays in the large drum
- The dryer shows OP again on the next try
Possible causes
Listed in Cissell's documentation
- A loose thermistor plug or corroded contacts
- A broken wire along the sensor lead
- Lint packed around the thermistor
- A failed sensor input on the micro control
Other likely causes — what usually sits behind error code OP on this control. A technician confirms which one it is before any part is replaced.
- A long lead that has been stretched by a drum or panel that was moved for cleaning
- Contacts in the plug that have corroded from the damp air of a laundry room
- A thermistor tip that has snapped from the clip after years of heat cycles
Safe checks before calling for service
- Switch the dryer off at the disconnect and let the big drum cool.
- Empty the lint screen and clean the lint door area.
- Do not reach behind panels or pull on wires.
- Restore power and try one cycle, then call us if OP shows again. Tell us the load that was inside.
How a technician diagnoses error code OP
- Read the code and confirm that OP appears at start or after warm-up.
- Inspect the thermistor, its plug and lead for wear, corrosion and lint.
- Measure the thermistor resistance cold and compare it with the chart.
- Check the micro control input with a known resistor.
- Replace the thermistor, lead or control only after the readings show which one has failed.
- The sensor lead runs through hot areas of a large cabinet, behind panels with line voltage.
- A resistance test needs the sensor disconnected and a meter.
- A large drum stays hot for a while, so work has to wait until it cools.
How error code OP differs from similar codes
The OPL control shows EoP for an open thermistor. The micro control on the 120 and 170 lb dryers shows OP, and SH for a short.
Technical reference
- Document
- Tumble Dryers 120/170 lb Troubleshooting TMB1268C, Part No. 70399901R2, Dec 2016 (pp.53, 65)
- Edition
- Part No. 70399901R2, December 2016; models through serial no. 0907000048
- Models / control
- 120/170 lb tumble dryers micro control (C-prefix models)
- Section
- Hybrid Timer Control Troubleshooting - 31. Error Codes, printed p. 53 (PDF p. 55); On Premise Micro Control (RM) Troubleshooting - 36. Error Codes, printed p. 65 (PDF p. 67)
- 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 Cissell dryer error codes
Can I take the wet load out of the drum?
Yes, once the drum has cooled. Move it to another machine.
Is OP the same as SH?
No. OP is an open circuit and SH is a short. Both are problems with the same sensor circuit.
Will OP clear by itself?
Only if a loose plug seats again. It usually returns until the circuit is repaired.
Need help with Cissell error code OP?
A technician confirms the cause on site and gives you the price in writing before any work starts.