True Refrigeration Error Codes — Complete Fix Guide

Error Code: True Refrigeration

What it means: True Manufacturing produces some of the most widely used commercial refrigerators and freezers in the foodservice industry — reach-in coolers, undercounter units, prep tables, and merchandising cases. True units with electronic controllers display fault codes as alphanumeric codes (E1–E9, F1–F9, and others) when a component or sensor fault is detected.

This guide covers the most common True Refrigeration error codes and their fixes.

True Refrigeration Error Code Reference

| Code | Meaning | Common Cause | | ------ |---------|-------------| | E1 | Return air sensor (room probe) fault | Failed or disconnected NTC probe | | E2 | Evaporator coil sensor fault | Probe failure, ice buildup over sensor | | E3 | Condenser sensor fault | Probe failure or disconnection | | E4 | Discharge line temperature fault | Probe failure, actual high discharge temp | | E5 | Ambient temperature sensor fault | Controller or sensor issue | | F1 | High temperature alarm | Product zone temp too high — door left open, condenser dirty | | F2 | Low temperature alarm | Freezer over-cooling, stuck defrost, sensor fault | | F3 | Defrost timeout alarm | Defrost heater failure, stuck defrost termination thermostat | | dF | Currently in defrost cycle | Normal state — not an alarm | | Hi | High temperature cutout active | Compressor safety shutdown due to high temp |

Common Causes (E1/E2 — Most Frequent)

• Failed NTC temperature probe — True units use NTC 10kΩ thermistors. Probes in wet, cold environments fail due to moisture intrusion and corrosion.
• Probe physically dislodged — Heavy loading or cleaning can knock a probe clip loose from the evaporator or air stream location.
• Wiring fault at controller — Wire pulled from terminal block, terminal loose, or wire broken at the connector crimp.
• Controller board failure — After a power surge or years of service, the analog input circuit on the True controller can fail.

Step-by-Step Fix for E1 / E2 Sensor Faults {#step-by-step-fix}

1. Identify which probe is faulting. E1 = return air/room sensor, E2 = evaporator coil sensor. Both use identical NTC 10kΩ probes in most True models, but they’re mounted in different locations.

2. Locate the faulting probe. E1 (room probe): typically mounted in the return air flow, clipped to a bracket inside the cabinet. E2 (evaporator probe): clipped directly to the evaporator coil fins, often visible through the evaporator cover panel.

3. Inspect probe and wiring. Check the full length of probe wire for damage. Confirm the probe tip is seated in its clip and making contact with the target surface. Confirm the wire ends are firmly seated in the controller terminal block.

4. Measure probe resistance. Disconnect the probe from the controller and measure resistance across the leads. At 35°F (2°C), expect 20,000–25,000 Ω. At 0°F (-18°C), expect 80,000–100,000 Ω. Open (OL) or shorted (0 Ω) = bad probe.

5. Replace the probe. True-compatible NTC 10kΩ probes are widely available. Snap the replacement into the same mounting clip and confirm the lead reaches the controller terminal block without tension on the wire.

Step-by-Step Fix for F1 / High Temperature Alarm

1. Check door gaskets. Pull the door closed and feel around the edges for cold air escaping. A damaged gasket is the most common cause of a reach-in failing to hold temperature.

2. Clean the condenser coil. Pull the refrigeration unit away from the wall (or remove the kick plate on undercounters) and inspect the condenser coil. Vacuum or brush off dust and debris. A dirty condenser causes head pressure to rise and reduces the unit’s ability to pull down temperature.

3. Check condenser fan operation. With the unit running, confirm the condenser fan is running. A seized fan motor causes rapid temperature rise.

4. Verify defrost is completing normally. A unit stuck in defrost (F3 or dF that doesn’t clear) won’t cool until defrost ends. Check the defrost termination thermostat and the defrost heater.

Parts That May Need Replacement {#parts-that-may-need-replacement}

Related Articles

• True Refrigeration E1 Error Code — Causes & Fix
• True Refrigeration E2 Error Code — Causes & Fix
• True Refrigeration E3 Error Code — Causes & Fix
• True Refrigeration E4 Error Code — Causes & Fix
• True Refrigeration E5 Error Code — Defrost Sensor Causes & Fix

See Also

• True TSSU Prep Table Error Codes, Causes, and Fixes
• True Refrigeration E1 Error Code — Causes & Fix
• True Refrigeration E5 Error Code — Defrost Sensor Causes & Fix
• True GDM-49 Glass Door Merchandiser Error Codes - Full Fault Guide