AHT Cooling Systems E33 Error Code
E34 E35 (software de seguranca) Pressao de aspiracao demasiado baixa Sobreaqueci
Source: vento-spi__aht-vento-iom.pdf
What does AHT Cooling Systems E33 mean?
The controller reports that superheating is too low. Superheat is the difference between actual suction gas temperature and the saturation temperature at suction pressure. Too-low superheat means liquid refrigerant is returning to the compressor (flood-back), which dilutes compressor oil and damages compressor valves and pistons. The controller shuts the compressor down to prevent damage.
Symptoms
- E33 displayed with red LED and buzzer active.
- Compressor shuts down on low superheat protection.
- Suction line may have frost or condensation further back than normal.
- Cabinet temperature rises without refrigeration.
Common causes
- EEV overfed — expansion valve opening too large relative to load.
- EEV control parameters set incorrectly (superheat target too low).
- Suction gas temperature sensor reading incorrectly (sensor fault producing false low superheat).
- Refrigerant overcharge — excess refrigerant causes liquid return.
- Sudden load reduction causing temporary liquid slugging before EEV responds.
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Diagnostic steps
Move goods and log the fault
Transfer perishable goods to another suitable cabinet. Record the fault code and device information.
Verify suction temperature sensor
Confirm the suction manifold sensor (E02 fault monitors this) is correctly positioned, not iced over, and reading accurately. A mislocated sensor produces false low superheat readings.
Check EEV operation
Verify EEV stepping and control signal. An EEV stuck in a large opening position overfeeds the evaporator and causes liquid return.
Assess refrigerant charge
A certified technician should check subcooling and suction conditions to determine if refrigerant overcharge is a contributing factor.
Review EEV control settings
Confirm superheat target and EEV control parameters in the controller against the AHT service commissioning data for the specific cabinet model.
Contact AHT service
Refrigerant charge adjustment and EEV recalibration require a certified AHT technician. Contact 00800/73783248 or www.aht.at/service.
When to call a professional
Low superheat faults involve refrigerant charge balance and EEV calibration, both of which require an AHT-certified technician. Repeated E33 without obvious sensor cause indicates a compressor is at risk — contact AHT service at 00800/73783248 or www.aht.at/service immediately.
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Other AHT Cooling Systems Error Codes
Fault in electronic expansion valve E01 Fault in suction pressure sensor E02 Fau
Fault in air intake sensor E04 Fault in air outlet sensor E05 Fault in slat sens
Fault in high-pressure sensor E07 Fault in compressor safety chain E08 Fault in
Fault in internal temperature sensor (Goods room) E10 Supply voltage too low/too
Low battery voltage (see → Chapter 10.2.3) E12 Fault in software class B (safety
Fault in EEPROM (control board defective) E32 Suction pressure too low E33 Super
Superheating too high E35 Internal temperature too high (goods room) E36 Interna
Control temperature too low E38 Control temperature too high E39 Run-time fault
Fault in internal memory E41 Heating gas temperature too high (pressure tube sen
Time-out Valve opening 100% E43 Condensation pressure too high E44 External alar
E03 E04 E05 E06 E07 Falha no sensor de temperatura do gas de succao (sensor do c
compressor Falha no sensor de temperatura do pressao) E10 E09 gas térmico (senso
Sources: www.aht.at