UniMac Washer Error Code E oP: Open Temperature Sensor
E oP means a UniMac washer-extractor reads its temperature sensor circuit as open, which usually points to a broken wire, an unplugged connector or a failed sensor. The wash water is normal; the machine just cannot read it. Dismiss the code as the manual describes, avoid heated washes, and call us if E oP returns.
Medium: the machine can still run cold cycles, but it cannot control wash temperature.
What does UniMac error code E oP mean?
E oP is the open temperature sensor error on UniMac QN washer-extractors and on the UC-series and UW pocket hardmount washer-extractors. The temperature sensor is a part whose resistance changes with water temperature, and the control reads that resistance through a small circuit. If the wire is broken, the plug has come loose or the sensor has failed, the circuit no longer completes. The control reads that as open, and on the UC and UW controls anything below 0 F is treated as an open circuit. Because the real water is nowhere near that cold, the control knows the reading cannot be right and stops trusting it. On QN machines the code appears when the cycle ends, and the heater stays off for the remainder of the cycle, so the load is washed without the heat it was meant to have. The error describes the sensor circuit, not the water in the tub.
Affected models and control systems
E oP is listed for UniMac QN washer-extractors (CHM1792C family), UC-series washer-extractors (CHM495R family, 20-100 lb) and UW/UWL/UWN/UWU 035-125 pocket hardmount washer-extractors (PHM1263R family). The limit of 0 F applies to the UC and UW controls.
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
- E oP appears on the display, on QN machines at the end of the cycle
- Hot washes come out lukewarm or cold
- The heater does not come on for the rest of a QN cycle
Possible causes
Listed in UniMac's documentation
- Temperature sensor plug that is not seated fully
- Sensor wiring that is broken or chafed through
- Failed temperature sensor reading as open
- Control input that cannot see the sensor circuit
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.
- A sensor lead stretched or pinched where it passes the tub or cabinet, after a service panel was reinstalled
- Heat and moisture cycling gradually corroding the sensor plug pins in a steamy laundry room
Safe checks before calling for service
- On a QN machine, opening the door or pressing a key dismisses the code when the cycle ends.
- On other machines, power down and back up.
- Look only at what is visible: confirm nothing is leaning on the machine's rear cables.
- If E oP comes back, stop heated washes and call us.
How a technician diagnoses error code E oP
- Read the code and the temperature display, and note the model and control generation.
- With power off, inspect the sensor connector and the wiring run for breaks, chafing and loose pins.
- Measure the sensor resistance at the plug and compare it with the manual's chart for the water temperature.
- Check the control's sensor input after the sensor and wiring pass the resistance test.
- Replace the sensor or repair the wiring, then run a heated cycle and confirm the temperature rises as expected.
- Reading the sensor circuit means disconnecting plugs and using a meter on a machine that carries 208-240 V behind the panels.
- A broken wire, a loose plug and a failed sensor give the same open reading, so the wiring has to be tested end to end.
How error code E oP differs from similar codes
E oP is the open circuit message; E SH is its opposite, a shorted sensor that the control reads as extreme heat. The two use different limits on UC and UW controls.
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 washer error codes
Does E oP mean the water is freezing?
No. The control sees an open circuit and reads it as an impossibly low temperature. The wash water is normal.
Can I keep washing cold loads?
Often the cycle can finish, but the machine cannot manage heat. For linens that need a hot wash, wait for the repair.
What is the difference between E oP and E SH?
E oP means the sensor circuit reads open. E SH means it reads shorted. Both mean the control cannot trust its temperature reading.
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.