True E3

What does True E3 mean?

The LAE electronic controller on your True TSCI-series scientific refrigerator has detected a fault on the T3 multifunction probe. T3 is an optional yellow NTC thermistor used as a secondary measurement point — on TSCI scientific units it typically monitors a glycol bottle or a secondary zone. E3 appears when the controller reads an open or short circuit on the T3 input. The T3 probe is not installed or activated on all TSCI models.

Symptoms

• The LAE display flashes 'E3' with the alarm indicator lit.
• Audible alarm beeps repeat from the controller until the fault is cleared.
• Scrolling to t3 via the Info button returns no reading or an implausible temperature.
• The cabinet may continue cooling normally via T1, but secondary zone temperature logging is disrupted.

Common causes

• Failed or open-circuit T3 NTC thermistor — most common cause; probe element has broken open.
• Disconnected or damaged T3 probe wiring between the sensor and the LAE T3 controller terminal.
• T3 connector not fully seated on the controller board, causing intermittent open-circuit detection.
• Moisture or contamination at the T3 connector producing false open readings.
• T3 probe activated in controller parameters but no probe is physically wired to the T3 input.

Diagnostic steps

1. 01

   Confirm T3 is installed on this unit

   Press the Info button and scroll through t1, t2, t3 — if t3 does not appear, the probe is not configured. An unexpected E3 in this case requires verifying controller parameters; contact True technical support at 855-372-1368.

2. 02

   Disconnect mains power

   Pull the plug or trip the breaker before touching probe terminals — LAE keypad power-off does not de-energize all circuits.

3. 03

   Locate and inspect the T3 probe

   The T3 probe (yellow wire, current revision) may sit inside a glycol bottle or at a secondary cabinet location. Trace the yellow wire to the LAE T3 terminal and check for breaks, corrosion, or a dislodged connector pin.

4. 04

   Measure T3 probe resistance

   Disconnect the probe from the controller before measuring. At 32°F (0°C) the LAE NTC T3 probe reads approximately 27.22 kΩ. Infinite resistance confirms open-circuit failure; near-zero confirms a short — both require replacement.

5. 05

   Replace the T3 probe

   Install a True OEM T3 NTC thermistor matched to the LAE controller's NTC curve. Reconnect to the T3 terminal, ensure the connector is fully seated, and restore mains power.

6. 06

   Confirm E3 has cleared

   After restoring power, verify the LAE display no longer shows E3 and that t3 via the Info button returns a valid temperature. If E3 returns with a confirmed good probe, the LAE controller T3 input circuit has failed and the board requires replacement.

When to call a professional

Engage a licensed technician if the T3 probe is inside a sealed glycol bottle assembly requiring specialized handling, if E3 persists after a confirmed good OEM probe is installed (indicating a controller board fault), or if the unit uses R290 hydrocarbon refrigerant and refrigerant-side access is needed. Controller parameter changes to enable or disable the T3 input should be handled by a True-authorized service agent.