IPSO Tumble Dryer Error Code OP: Open Thermistor
OP on an IPSO 120/170 lb tumble dryer means the control reads an open thermistor: the temperature sensor looks disconnected or broken. Without a reading the control cannot regulate heat properly. If you smell gas, step outside and phone the gas utility from there; otherwise take the dryer out of use until it has cooled.
High: heat control is lost on a dryer with a gas or steam heat source.
- Code
- OP
- Maker
- IPSO
- Equipment
- Industrial laundry
- Applies to
- Tumble dryers 120/170 lb (TMB1268C family) micro control
What does IPSO error code OP mean?
The thermistor is a temperature sensor whose resistance changes with heat, and the control uses it to decide when to fire the heat and when to stop. If the circuit is open, because the sensor failed, a wire broke or a plug came loose, the control gets no valid reading and posts OP. It cannot regulate heat properly. Plant staff see a dryer that stops heating, over-dries or shuts down early. This applies to dryers such as the IPD120G2 gas model or the IPD170S2 steam model. The IPD series is an older line that plants still run. Gas models call for caution: a smell of gas means you go outside at once and phone the gas utility from there. Without a trusted temperature signal, running on is not safe for the load or the dryer.
Affected models and control systems
IPSO 120/170 lb tumble dryers in the TMB1268C family with the micro control, such as the IPD120G2 (gas) and IPD170S2 (steam). Other controller generations use different codes.
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 on the display
- Dryer stops heating or heats erratically
- Loads over-dry or come out cool and damp
- Dryer shuts down early
Possible causes
Listed in IPSO's documentation
- Open thermistor circuit
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 thermistor that has failed open
- A wire between the thermistor and control that is broken
- A thermistor connector that has come loose or corroded
- A sensor input on the control that reads open behind OP
Safe checks before calling for service
- If you notice a gas smell, step outside and phone the gas utility from there.
- Otherwise, take the dryer out of use until it has cooled.
- Do not pull any sensor plug yourself.
- Ask us to test the thermistor and its wiring.
How a technician diagnoses error code OP
- Read the code and confirm OP is steady.
- Let the dryer cool and shut off gas and power before touching anything.
- Inspect the thermistor plug and wire for breaks or corrosion.
- Measure thermistor resistance and compare it with a reference temperature.
- Test the control input, then replace the thermistor or harness as needed.
- The sensor sits in the air stream near the burner on gas models or the coil on steam models. Testing it means working with gas shut off and the control live. A wrong reading of the thermistor can leave a dryer running hot.
How error code OP differs from similar codes
OP is an open circuit. SH is the shorted circuit on the same sensor.
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
- Tumble dryers 120/170 lb (TMB1268C family) micro control
- 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 IPSO industrial laundry error codes
Can I keep drying with OP showing?
No. Without a valid temperature reading, the control cannot regulate heat safely.
Will OP clear when the dryer cools?
It may disappear, but an open circuit does not heal itself.
Is OP the same as SH?
No. OP is an open sensor circuit and SH is a shorted one.
Need help with IPSO error code OP?
A technician confirms the cause on site and gives you the price in writing before any work starts.