UniMac QN Washer-Extractor Error Code E PS: Pressure Sensor Error
E PS means a UniMac QN washer-extractor had no valid water level sensor input for 30 seconds. Switch the power off and back on, check that the hot and cold water supply is on, and call us if E PS returns.
Medium: the cycle halts without a level reading, but the cause is often a tube or connector.
- Code
- E PS
- Maker
- UniMac
- Equipment
- Industrial laundry
- Applies to
- CHM1792C family washer-extractor (QN models, 20-100 lb) front-end control
What does UniMac error code E PS mean?
E PS is the pressure sensor error on a UniMac QN washer-extractor such as the UCA020QN. The washer needs its pressure sensor to know how deep the water is. A tube runs from the tub to the sensor, and the sensor turns the air pressure in that tube into a level reading. The control had no valid water level sensor input for 30 seconds. Without a reading, fill and drain cannot be managed, so the cycle halts.
A kinked, water-filled or blocked tube between the tub and the pressure sensor is the first thing to suspect. A loose or corroded connector on the pressure sensor wiring can break the signal. A pressure sensor that no longer gives a valid water level reading is another. The control input that reads the pressure sensor signal is the last item on the list.
Switch the power off and back on. Do not open the cabinet to handle the sensor tube. Note whether the display shows any water level before you call.
Affected models and control systems
E PS is listed for the CHM1792C family washer-extractors, the QN models from 20 to 100 lb, with the front-end control; the manual's example model is the UCA020QN.
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 PS and the cycle stops
- The display shows no water level or a stuck level
- Fill or drain does not follow the usual pattern
- The code returns during the fill step
Possible causes
Listed in UniMac's documentation
- A kinked, water-filled or blocked tube between the tub and the pressure sensor
- A loose or corroded connector on the pressure sensor wiring
- A pressure sensor that no longer gives a valid water level reading
- The control input that reads the pressure sensor signal
Other likely causes — what usually sits behind error code E PS on this control. A technician confirms which one it is before any part is replaced.
- Soap residue or lint plugging the tube at the tub fitting
- Tube pulled off its fitting at the sensor
- Connector pins wet from a nearby leak
- Sensor diaphragm damaged by a pressure spike
Safe checks before calling for service
- Switch the power off and back on.
- Check that the hot and cold water supply is on.
- Do not open the cabinet to handle the sensor tube.
- If E PS returns, note whether the display shows any water level before you call us.
How a technician diagnoses error code E PS
- Read the code and note the level shown at the time.
- Lock out the machine and trace the sensor tube from tub to sensor.
- Blow the tube clear and check the tub fitting.
- Inspect the sensor connector and wiring.
- Compare the sensor output at empty and full.
- Replace the sensor only after the tube and wiring prove good.
- The sensor and tube sit inside the cabinet near live wiring.
- Clearing the tube while the tub holds water can spill into the electrics.
- Judging a sensor reading needs a meter and a controlled fill.
How error code E PS differs from similar codes
E PS is the pressure sensor giving no valid reading, while E LP and E Pr are the pressure switch checks in the test cycle.
Technical reference
- Document
- Washer-Extractor Programming CHM1792C_SVG, Part No. F8641001ENR4, Error Codes Table 29 (pp. 100-107)
- Maker documentation
- UniMac owner support
- Edition
- Part No. F8641001ENR4, January 2020
- Models / control
- CHM1792C family washer-extractor (QN models, 20-100 lb) front-end control
- Section
- Error Codes, Table 29, pp. 100-108 (PDF pages equal printed pages)
- 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 PS mean the tub is empty?
No. It means the control has no valid level reading, whatever the level is.
Could a blocked tube cause it?
Yes, it is one of the first things we check.
Will a restart fix it?
It may if the signal was briefly lost. If it returns, the sensor path needs testing.
Need help with UniMac error code E PS?
A technician confirms the cause on site and gives you the price in writing before any work starts.