Thermistor
Common temperature-sensing fault part. Confirm resistance range and connector.
True Refrigeration T-Series Error Codes — What They Mean
True Manufacturing T-Series reach-in refrigerators (T-23, T-35, T-49, T-72 and similar) are the most common commercial reach-in refrigerators in US foodservice. Their electronic controllers display error codes when a fault is detected. This guide covers the most common T-Series error codes and what to do about each one.
Common T-Series Error Codes
| Code | Meaning | Urgency |
|---|---|---|
| E1 | Cabinet air sensor fault | Medium — sensor replacement needed |
| E2 | High temperature alarm | High — product at risk |
| E3 | Defrost termination fault | Medium — heater or thermostat issue |
| dF | Defrost active | Normal — not a fault |
| HI | High temp alert (product temp) | High — door open or refrigeration failure |
Common Causes
- E1: Failed NTC air sensor — The cabinet temperature sensor has failed open or shorted. Controller can’t regulate without it.
- E2: Refrigeration system failure — Dirty condenser, failed condenser fan, low refrigerant, or a door that won’t seal properly.
- E3: Defrost heater or thermostat failed — Defrost couldn’t terminate properly. Either the heater didn’t work, or the termination thermostat failed to cut it off.
- HI: Extended door opening or sealed system fault — Product at risk; find root cause immediately.
Step-by-Step Fix
- For E1 (sensor fault) — Locate the NTC sensor (clipped to evaporator coil or cabinet interior). Test resistance: ~10kΩ at 77°F. Open or zero reading = replace. Use True OEM replacement sensor for your model.
- For E2 (high temp) — Check: (a) door gasket seals fully, (b) condenser is clean (pull unit out, vacuum fins), (c) condenser fan runs when compressor is on, (d) unit isn’t overstocked blocking airflow.
- For E3 (defrost fault) — Open rear panel to access the evaporator. If it’s heavily frosted, defrost has been failing. Test heater resistance (10–100Ω typical) and defrost termination thermostat (should be closed at room temp). Replace failed component.
- For HI alert — First, confirm product temperature. If product is warm, the unit has been failing for a while. Identify root cause: condenser, fan, refrigerant, or door seal.
- Reset after repair — Power cycle the unit (unplug 30 seconds). Confirm error code clears and the controller shows a valid cabinet temperature.
Parts Often Needed
| Part | Notes |
|---|---|
| NTC air sensor | True OEM only — controller is calibrated to specific sensor curve |
| Defrost heater | Match to model and voltage (115V or 208-230V) |
| Defrost termination thermostat | Clips to evaporator; opens at ~50°F to terminate defrost |
| Door gasket | True model-specific — measure and order by model number |
| Condenser fan motor | Replace if not running with compressor on |
Technician Tips
When diagnosing commercial refrigeration faults, start with the controller’s alarm history. Most digital controllers (Dixell, Carel, Eliwell) store the last 5-10 alarms with timestamps. An E1 alarm that appears consistently every few hours suggests a sensor going bad — the resistance value drifts until it’s out of range. An intermittent HI/LO alarm that appears only during hot afternoons suggests a condenser issue, not a sensor fault.
Prevention: Schedule quarterly condenser coil cleaning. Dirty coils are the #1 cause of high-head-pressure faults and compressor overheating in commercial refrigeration. Use a soft brush and compressed air — never a pressure washer on the coil fins.
Need Replacement Parts?
Before ordering, match the refrigeration part to the model number, electrical rating, and failure symptom. Check current prices on Amazon - prices and availability change frequently.
When to Call a Pro
If the condenser is clean, sensors and heaters test good, and the unit still can’t hold temperature, the sealed refrigeration system (compressor, TXV, refrigerant) needs a certified tech with recovery equipment.