AHT Cooling Systems E08

What does AHT Cooling Systems E08 mean?

The controller detects a fault in the heating gas temperature sensor (pressure tube sensor). This probe monitors the discharge gas temperature at the pressure tube (hot gas line) exiting the compressor. An open-circuit, short-circuit, or out-of-range reading triggers E08, disabling discharge temperature protection.

Symptoms

• E08 fault code displayed with red LED and buzzer active.
• Discharge gas temperature monitoring disabled.
• Compressor protection against overheating may rely on mechanical devices only.
• Cabinet temperature regulation may be affected.

Common causes

• Pressure tube sensor (discharge temperature sensor) open-circuit or short-circuit failure.
• Sensor lead damaged by heat or physical contact with hot compressor discharge line.
• Loose or corroded connector at sensor or control board.
• Sensor clamp shifted from the pressure tube, causing inaccurate and out-of-range readings.
• Control board input channel failure.

Diagnostic steps

1. 01

   Protect goods and log fault

   Move perishable goods to a correctly rated cabinet. Record fault code and device serial number.

2. 02

   Locate the pressure tube sensor

   Find the temperature probe clamped to the discharge line (pressure tube) close to the compressor outlet per AHT Vento service documentation.

3. 03

   Check sensor mounting and wiring

   Confirm the sensor is securely clamped to the hot gas line and its lead is routed away from excessive heat sources. Reseat connectors.

4. 04

   Test sensor resistance

   Disconnect the sensor and measure resistance at ambient temperature with a multimeter. Compare to the NTC curve; open or short confirms failure.

5. 05

   Replace the sensor

   Fit an AHT-approved discharge temperature sensor in the correct clamped position on the pressure tube.

6. 06

   Clear fault and verify operation

   Restore power, confirm E08 clears, and run for 2 hours before reloading goods.

When to call a professional

The discharge line sensor is mounted on a high-temperature, high-pressure refrigerant line. Contact an AHT-authorized technician at 00800/73783248 or www.aht.at/service for replacement if the sensor mounting is in a confined compressor compartment.