AHT Cooling Systems E43

What does AHT Cooling Systems E43 mean?

The controller reports that condensation pressure is too high. The high-pressure sensor (monitored under E06) has measured a condensing pressure above the configured alarm threshold. High condensation pressure reduces compressor efficiency, increases discharge temperature, and — if left uncorrected — will eventually trip the mechanical high-pressure cut-out and shut the compressor down. E43 is the controller's early warning before a full compressor safety trip (E07).

Symptoms

• E43 fault code displayed with red LED and buzzer active.
• Condensation pressure reading above the high-pressure alarm threshold.
• Compressor may still be running but under stress — discharge line will be very hot.
• Cabinet cooling capacity reduced — goods room temperature may begin rising.
• High-pressure mechanical cut-out (E07) may follow if condition is not corrected.

Common causes

• Condenser coils dirty or blocked with dust and grease, severely restricting heat rejection.
• Condenser air discharge obstructed — objects placed on top of or against the cabinet blocking warm air exhaust.
• Store ambient temperature too high, reducing the temperature differential between refrigerant and room air.
• Condenser fan motor failed or running slowly, reducing airflow across the condenser.
• Refrigerant overcharge causing excessively high condensing pressure at normal ambient conditions.
• High-pressure sensor fault producing false high readings (check against mechanical gauge if available).

Diagnostic steps

1. 01

   Check and clear condenser

   Inspect condenser coils and grilles for dust and debris. Clean the condenser per the AHT Vento cleaning procedure — this is the most common cause of high condensation pressure and can often resolve E43 immediately.

2. 02

   Ensure adequate ventilation around the cabinet

   Verify that there is at least 60 mm clear space above the cabinet for warm air exhaust. Remove any objects, signs, or obstructions placed on top of or blocking condenser airflow.

3. 03

   Check condenser fan operation

   Confirm the condenser fan is running at normal speed. A failed or slow fan significantly reduces heat rejection. Listen for unusual noise and feel for airflow at the condenser discharge.

4. 04

   Verify ambient temperature

   Check that the store temperature is within the rated ambient class for the device. High ambient temperatures above the cabinet's rated maximum will elevate condensing pressure.

5. 05

   Monitor pressure after corrective action

   After cleaning the condenser and removing obstructions, allow the cabinet 30 minutes to stabilize. If E43 clears and stays clear, the fault was condenser-related.

6. 06

   Contact AHT service if E43 persists

   If condensation pressure remains high after cleaning and ventilation checks, contact AHT service at 00800/73783248 or www.aht.at/service. Refrigerant charge assessment, fan replacement, or sensor replacement requires an authorized technician.

When to call a professional

If E43 persists after condenser cleaning and airflow checks, an AHT-authorized technician is required to assess refrigerant charge, condenser fan, and high-pressure sensor. On R-290 units, all refrigerant circuit work requires flammable-refrigerant certified personnel. Contact AHT service at 00800/73783248 or www.aht.at/service.