UniMac Washer-Extractor Error Code E d 51: Inrush Control Pin Check

What does UniMac error code E d 51 mean?

When power is first applied to a UniMac QN washer-extractor such as the UCA020QN, the drive has to limit the surge of current that rushes in to charge its internal parts. A pin on the drive board controls that limit. E d 51 is the inrush pin hardware on-off check failing. The drive tested the pin and did not get the result it expected, so it stopped the cycle.

The maker's operator step is to cut the power, and that clears the display. This can give a false sense that all is well, because the board problem underneath can return and halt the next batch. A failure of the inrush limiting circuit is the likeliest cause. A loose or burned connector at the drive board is another. Unstable supply voltage at the moment power is switched on can also upset the check. A board that fails the check again and again will need replacing.

Affected models and control systems

E d 51 is listed for the CHM1792C family washer-extractors, the QN models from 20 to 100 lb, with the front-end control and drive board; 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 d 51 shortly after power-up
• The code clears with a power cycle but comes back later
• A click or odd delay as the drive powers up
• No motor action when the cycle starts

Possible causes

Listed in UniMac's documentation

• A failure of the inrush limiting circuit on the drive board
• A loose or burned connector at the drive board
• Unstable supply voltage at the moment power is switched on
• A drive board that repeatedly fails the inrush pin check

Other likely causes — what usually sits behind error code E d 51 on this control. A technician confirms which one it is before any part is replaced.

• Relay contacts in the inrush circuit pitted from many power cycles
• Supply that sags when other machines start at the same time
• Heat discoloration around the connector that raises its resistance
• Control wire to the inrush pin broken inside its insulation

Safe checks before calling for service

How a technician diagnoses error code E d 51

1. Read the code and note whether it follows power-up.
2. Measure supply voltage at the moment of switch-on.
3. Inspect the drive board connectors for heat marks and looseness.
4. Observe the inrush circuit at power-up if the machine allows it safely.
5. Replace the drive board when the check fails on a stable supply.

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.