UniMac Washer Error Code Eio 42: Door Lock Input Pin
Eio 42 on a UniMac QN washer-extractor is an I/O board hardware code for the door lock input pin, the pin through which the board learns whether the door is locked. If it fails its check, the board cannot confirm the lock state and the control stops the cycle. Turn the washer off, never bypass the door switch, and call us.
High: the lock state cannot be confirmed, so the cycle stops for safety.
What does UniMac error code Eio 42 mean?
Eio 42 on UniMac QN washer-extractors such as the UCA020QN is an input and output board hardware code for the door lock input pin. The board does more than power the lock. It also reads back whether the door is actually locked, and it does that through the door lock input pin. This reading is what lets the control start a spin only when the door is proven shut. If the pin fails its check, the board cannot confirm the lock state, and the control stops the cycle for safety. The code stays until the board is checked. The manual lists a broken or loose wire on the door lock input signal, worn or dirty contacts inside the lock switch, and a failed input circuit on the I/O board for the lock.
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 42 on the display and the cycle stops
- Door appears closed but the machine does not recognize it
- Lock seems to latch, yet the cycle will not begin
- Code returns every start
Possible causes
Listed in UniMac's documentation
- Broken or loose wire on the door lock input signal
- Worn or dirty contacts inside the lock switch
- Failed input circuit on the I/O board for the lock
Other likely causes — what usually sits behind error code Eio 42 on this control. A technician confirms which one it is before any part is replaced.
- Lint and detergent residue on the lock switch contacts at the door
- A switch wire fatigued by the door opening and closing all day
- Door closing slightly out of line so the switch only makes contact now and then
Safe checks before calling for service
- Write down Eio 42 and the door's behavior.
- Turn the washer off and let the drum settle.
- Never bypass the door switch.
- Call us to test the input circuit.
- Keep the area around the washer clear.
How a technician diagnoses error code Eio 42
- Read the code and note whether the door feels latched.
- Check the door and latch alignment and clean the visible lock contacts with power locked out.
- Inspect the lock switch wire and connector for breaks.
- Measure the lock input signal at the board with the door open and closed.
- Replace the lock switch, wire or board, whichever fails the measurement.
- The lock input is part of a safety interlock, and bypassing it to get a cycle running is dangerous.
- Reading the signal at the board means working in the cabinet with the control energized.
- Dirty contacts, a broken wire and a failed input circuit give the same code and need testing in order.
How error code Eio 42 differs from similar codes
Eio 42 is the door lock input, how the board reads the lock. Eio 30 to 37 are about the outputs that drive the lock.
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
Why does the washer not know the door is closed?
The input that reports lock state is failing its check, so the board cannot confirm it.
Can I bypass the door switch?
No. It is a safety interlock and must stay in place.
Is the lock itself worn?
It might be. Contacts inside the lock switch are on the manual's list, but wiring and the board are too.
Need help with UniMac error code Eio 42?
A technician confirms the cause on site and gives you the price in writing before any work starts.