True cabinet temperature sensor probe
Part: T-84984
Exact probe part cited for E1 cabinet sensor faults; verify connector style before ordering.
$15-$25
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True Refrigeration Error Codes
True refrigeration is the most common brand in restaurant reach-in coolers and freezers. T-Series, T-49, and GDM series use a digital controller with error codes displayed on the front panel.
True Error Code Table (All Series)
| Code | Fault | Common Cause | Action |
|---|---|---|---|
| E1 | Cabinet sensor failed | Temperature probe open/short | Replace temp sensor, check wiring |
| E2 | Evaporator sensor failed | Coil sensor fault | Replace evap sensor, check connector |
| E3 | Condenser sensor failed | Condenser temp sensor fault | Replace condenser sensor |
| E4 | Controller fault | Main board failure | Replace controller |
| HI | High temperature alarm | Cabinet too warm | Check door seal, condenser, system |
| LO | Low temperature alarm | Cabinet too cold | Check thermostat setting, controller |
| dF | Defrost in progress | Normal defrost cycle | None - normal operation |
| d1 | Defrost sensor fault | Defrost termination failed | Check defrost sensor, termination |
| AL | Alarm condition | Any alarm active | Check cabinet temp, resolve cause |
| CF | Controller configuration | Settings lost | Reconfigure controller parameters |
Most Common True Refrigeration Faults
E1 - Cabinet Temperature Sensor Failure
The most common True fault code. The cabinet temperature probe is a thermistor, so resistance changes with temperature. When the controller reads a resistance outside the valid range (open or short), it defaults to continuous compressor run to protect the food.
The thermistor is a small probe mounted in the evaporator housing. It’s a standard 10K ohm NTC thermistor at 77 degrees F. As temperature drops, resistance increases. At 40 degrees F (typical cooler temp), it should read about 10-15K ohms. An open circuit (OL) or short (0 ohms) means the probe has failed. True replacement part T-84984 (~$15-25).
Tip: the wiring from the probe to the controller runs through the cabinet insulation and is often damaged by sharp edges in the evaporator housing. Before replacing the probe, check the connector at the controller and look for chafed wires.
HI - High Temperature Alarm
HI on the display means the cabinet is too warm. This is not a sensor failure, because the temperature probe is working. The compressor can’t keep up. First check: the condenser coil. True reach-ins have a condenser coil on the back or bottom that packs with dust and grease in restaurant kitchens. Clean it with a stiff brush and vacuum. A clogged condenser is the cause of about 80% of high-temperature alarms on True units.
Second check: the condenser fan motor. On T-Series, the fan should be running whenever the compressor runs. A failed fan motor means no airflow across the condenser, causing high head pressure and warm cabinets. True fan motors (part T-04523, ~$45-70) are standard 1/20 to 1/15 HP shaded-pole motors.
LO - Low Temperature Alarm
The cabinet is too cold. This usually means the temperature controller setting is wrong, the controller has failed in the on mode, or the evaporator fan is running continuously. On True freezers, check the defrost settings first. If the defrost happens too infrequently, ice builds on the evaporator and prevents proper airflow.
dF - Defrost in Progress
This is not a fault. The True controller shows dF during the defrost cycle (typically 15-30 minutes, 3-4 times per day on freezers). The compressor stops and the heaters cycle on to melt frost from the evaporator coil. If dF stays on for more than 45 minutes, the defrost termination sensor has failed and the freezer is stuck in defrost. Check the d1 code.
Parts Reference
| Part | Fits | Cost |
|---|---|---|
| Cabinet temp sensor | All T-series | $15-$25 |
| Condenser fan motor | T-49, GDM series | $45-$70 |
| Temperature controller | T-Series | $60-$120 |
| Evaporator fan motor | T-Series | $30-$55 |
| Defrost timer/controller | Freezer models | $50-$90 |
| Condenser coil brush | All | $5-$10 |
| Door gasket | Per model | $40-$80 |
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.