UniMac Washer Error Code Eio 29: I/O Board Mosfet Enable
Eio 29 on a UniMac QN washer-extractor means the I/O board reported a hardware failure at its Mosfet enable pin, so the control stopped the cycle. Write down the code and what the washer was doing, switch the machine off with the cabinet closed, and look for water on the floor. Then call us with the model number.
High: the control stops the cycle because the board cannot safely switch its outputs.
What does UniMac error code Eio 29 mean?
Eio 29 appears on UniMac QN washer-extractors such as the UCA020QN when the input and output board reports a hardware failure at its Mosfet enable pin. A Mosfet is an electronic switch, and on the I/O board these switches power outputs such as the water valves and the door lock. An enable pin tells the Mosfet stage that it is allowed to switch. The board checks that this pin responds the way it should. If the enable pin does not respond as expected, the board cannot safely switch those outputs, so the control stops the cycle and holds the code. This is a hardware code from the board's own check, so it needs a technician. The manual lists the I/O board connectors and power supply to it, the wiring harness at the board, moisture or corrosion on the board, and the I/O board itself if the code returns.
Affected models and control systems
Listed for the CHM1792C family of UniMac QN washer-extractors (20-100 lb), with the UCA020QN as the example model, on the input and output (I/O) board.
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
- Eio 29 on the display and the cycle stops
- Valves or the door lock do not respond
- The code returns after a restart
- Damp floor or condensation near the machine
Possible causes
Listed in UniMac's documentation
- I/O board connectors and power supply to it
- Wiring harness condition at the board
- Moisture or corrosion on the board
- I/O board itself if the code returns
Other likely causes — what usually sits behind error code Eio 29 on this control. A technician confirms which one it is before any part is replaced.
- Water from a leaking hose or a washdown reaching the lower cabinet
- A power-supply connector to the board with a high-resistance contact
- A board worn by heat cycles beside the valves
Safe checks before calling for service
- Write down the full code, Eio 29, and what the washer was doing when it appeared.
- Switch the machine off at its power control and leave the cabinet closed.
- Look at the floor for water, since moisture near the board can cause board errors.
- Ring us with the code and the model number in hand.
- Keep wet items and cleaning sprays away from the cabinet.
How a technician diagnoses error code Eio 29
- Read the full code and history on the display.
- With power locked out, inspect the I/O board connectors and harness for looseness, corrosion and moisture.
- Verify the board's supply and ground with a meter.
- Clean and dry the board and reseat connectors if moisture is found, and retest.
- Replace the I/O board only if the code returns with clean connections and power.
- The I/O board switches line-voltage loads, so its supply and outputs are tested with a meter on live 208-240 V circuits.
- Moisture damage can be hidden under connectors and needs a close inspection with the cabinet open.
- A board that fails its own hardware check should be replaced with the right part and verified under a full cycle.
How error code Eio 29 differs from similar codes
Eio 29 is the Mosfet enable pin. Eio 33 reports the Mosfet enable hardware itself, and Eio 30 to 35 cover the door lock outputs.
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 washer error codes
Is Eio 29 the same as E nr?
No. E nr is a communication loss with the I/O board. Eio 29 is the board reporting its own hardware check failed.
Can I reset it?
A restart will clear the display, but the check will fail again if the cause remains.
Is moisture really a cause?
Yes. The manual lists moisture or corrosion on the board.
Need help with UniMac error code Eio 29?
A technician confirms the cause on site and gives you the price in writing before any work starts.