Randell Prep Table Error Code E04: S4 Sensor Failure

What does Randell error code E04 mean?

The fourth sensor input on the Danfoss controller is S4. When its reading is lost, the display shows E04, and the owner's manual says to contact service. Depending on the table, that sensor may help manage defrost or temperature limits, so the table may run with less protection until the sensor is replaced. In practice that means the controller cannot confirm that a defrost has finished, or cannot enforce a limit that would normally stop an overshoot. The compressor may keep running normally for days, which hides the problem. The listed causes are the S4 sensor and its plug, the wire run to the controller, the S4 input on the controller, and frost or water around the sensor. Frost or water around a sensor lead is a pattern with defrost-related sensors, since they sit in the coldest and wettest part of the cabinet. The code does not tell you which of those caused it. A technician reads the sensor, then the wire, then the input, in that order, so a good controller is not replaced for a wire problem.

Affected models and control systems

This applies to Randell 8000-290 and 9000W-290 series prep tables with the Danfoss controller, such as the 8148N-290 and 9148W-290. Other controller generations use other sensor numbering.

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

• E04 on the controller display
• Pans at the back of the well drifting warm
• Frost thicker than usual on the coil
• No change in normal running, which can hide the problem

Possible causes

Listed in Randell's documentation

• S4 sensor and its plug
• Wire run to the controller
• S4 input on the controller
• Frost or water around the sensor

Other likely causes — what usually sits behind error code E04 on this control. A technician confirms which one it is before any part is replaced.

• Sensor lead stiffened and cracked from years of cold cycling
• Ice forming around the sensor mount and pulling it loose
• Drain backup that leaves standing water near the sensor

Safe checks before calling for service

How a technician diagnoses error code E04

1. Read the code and confirm S4 is named.
2. Compare back-of-well pan temperature with the controller display.
3. Inspect the S4 sensor and lead for ice, water and cracks.
4. Check wire continuity to the controller.
5. Measure sensor resistance at a known temperature.
6. Replace the failed part and confirm defrost and temperature behave normally.

How error code E04 differs from similar codes

E04 names the S4 input. E01, E02 and E03 name S1, S2 and S3 on the same controller.

Technical reference

Document

Randell 8000-290 & 9000W-290 Series Prep Tables Operator Manual, PP MNL1803 Rev. I (12/25), Carel / Danfoss controller codes

Edition

PART NUMBER PP MNL1803, REV. I (12/25)

Models / control

Danfoss controller (8000-290 / 9000W-290)

Section

Carel Controller Codes and Danfoss Controller Codes tables, Service/Troubleshooting, printed pp. 5-6

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.