UniMac Washer-Extractor Error Code E oP: Sensor Circuit Open
E oP means the temperature sensor circuit is open on a UniMac QN, UC-series or UW washer-extractor. Clear it as the model requires, avoid heated washes and call us if it returns.
Medium: the machine can still run cold cycles, but heated washes are not reliable.
- Code
- E oP
- Maker
- UniMac
- Equipment
- Industrial laundry
- Applies to
- CHM495R family washer-extractor front-end control (20-100 lb) / PHM1263R family pocket hardmount washer-extractor (UWL/UWN/UWU 035-125) front-end control / CHM1792C family washer-extractor (QN models, 20-100 lb) front-end control
What does UniMac error code E oP mean?
UniMac QN, UC-series and UW pocket hardmount washer-extractors show E oP when the temperature sensor circuit is open. An open circuit usually means a broken wire, an unplugged connector or a sensor that has died. The control reads the sensor as a resistance. When the reading says the circuit is not complete, the control cannot tell how warm the water is. UC and UW controls call anything below 0 F open. On QN machines the message shows at the end of the batch and the heater stays off until the cycle is over.
A sensor connector that is not seated fully is the easiest cause. A sensor wire broken or chafed through is another. A temperature sensor that has died would produce the same reading. A control input that reads the sensor as open is the last possibility.
On a QN machine, open the door or press any keypad at the end of the batch to clear the code. On other machines, power down and then up.
Affected models and control systems
E oP is listed for the CHM495R family washer-extractors (UC series, 20 to 100 lb), the PHM1263R family pocket hardmount washer-extractors (UWL, UWN and UWU 035 to 125) and the CHM1792C family QN washer-extractors, all with the front-end control.
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
- The display shows E oP, on QN machines at the end of the batch
- Heated washes come out cold
- The cycle runs but the water never warms
- The code repeats on the next heated cycle
Possible causes
Listed in UniMac's documentation
- A sensor connector that is not seated fully
- A sensor wire broken or chafed through
- A temperature sensor that has died
- A control input that reads the sensor as open
Other likely causes — what usually sits behind error code E oP on this control. A technician confirms which one it is before any part is replaced.
- Sensor lead pulled tight when the machine was moved
- Wire insulation worn through where it crosses the tub edge
- Corrosion in the sensor plug from steam and detergent
- Control board input damaged by a surge
Safe checks before calling for service
- On a QN machine, open the door or press any keypad at the end of the batch to clear the code.
- On other machines, power down and then up.
- Only look at what you can see from outside, for example whether the rear cables are being squeezed.
- If E oP returns, stop heated washes and call us.
How a technician diagnoses error code E oP
- Read the code and note the control family.
- Lock out the machine and check the sensor connector.
- Inspect the sensor wire from end to end.
- Measure the sensor resistance and compare it with the temperature.
- Replace the sensor or repair the wire; check the control input if both are good.
- Sensor readings require opening the tub area and the control cabinet.
- Judging sensor resistance against temperature needs reference values.
- Replacing a sensor in the tub may involve draining and sealing.
How error code E oP differs from similar codes
E oP is the open-circuit reading, while E SH is the shorted-circuit reading on the same temperature sensor.
Technical reference
- Document
- Washer-Extractor Programming CHM495R_SVG, Part No. F8208501ENR10, March 2017, Error Codes (pp. 36-37)
- Maker documentation
- UniMac owner support
- Edition
- Part No. F8208501ENR10, March 2017
- Models / control
- CHM495R family washer-extractor front-end control (20-100 lb) / PHM1263R family pocket hardmount washer-extractor (UWL/UWN/UWU 035-125) front-end control / CHM1792C family washer-extractor (QN models, 20-100 lb) front-end control
- Section
- Error Codes table, pp. 36-37 (E Pr only on Design 1 models; Ed01-Ed11 on Design 2 and 3 models)
- 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 UniMac industrial laundry error codes
Does E oP mean the water is cold?
Not necessarily. The control cannot read the temperature, so it treats the sensor as missing.
Can I keep washing?
Cold washes only. Avoid heated cycles until we have checked the sensor.
How is E oP different from E SH?
E oP means open, E SH means shorted.
Need help with UniMac error code E oP?
A technician confirms the cause on site and gives you the price in writing before any work starts.