Common Reefer Container Alarms and What They Mean

Understand common reefer container alarms, what causes them, and how to respond before your perishable cargo is at risk.

Reefer containers are built to protect your perishable cargo — but when an alarm code appears on the control panel, it’s a sign something isn’t right. Knowing what these alarms mean, and how to respond quickly, can make the difference between a safe delivery and a spoiled shipment. This guide covers the most common reefer container alarms, their likely causes, and what to do next.

Understanding Reefer Alarms

Every modern reefer (Carrier, Thermo King, Daikin, etc.) includes onboard sensors that continuously monitor temperature, pressure, and electrical performance. When the system detects an abnormal reading, it triggers an alarm code displayed on the controller — like “AL02” or “AL44.”

Each alarm is ranked by severity:

⚠️ Advisory – Minor issue; reefer still cooling.

❗ Warning – Cooling performance may be affected.

🚫 Critical – Cooling stopped; immediate attention required.

Common Reefer Alarm Codes and Meanings

(Note: Code numbers vary slightly by brand. Always check the manufacturer’s alarm reference chart.)

Immediate Steps When an Alarm Appears

1. Do Not Ignore It Even minor alarms can escalate quickly — especially if the reefer is unplugged or waiting for pickup.
2. Record the Details Take a photo of:

The alarm code display

Container number

Date/time This record supports insurance or USDA/FDA documentation if product damage occurs.

1. Contact Reefer Support or Terminal Technicians At ports, request immediate inspection from a reefer technician. If on the road, contact your drayage dispatch for a genset swap or service stop.
2. Monitor Temperature Closely If the reefer remains powered, check that return and supply air readings stay near setpoint. If not, request transfer to a powered reefer yard or cold storage facility.

Preventing Reefer Alarms Before They Happen

Pre-trip inspection (PTI): Required before loading; checks for active alarms and sensor faults.

Keep air vents and coils clean: Dirt restricts airflow and causes pressure alarms.

Use calibrated sensors: Faulty thermistors trigger false alarms.

Secure electrical connections: Vibration during drayage often loosens power cables.

Fuel and service gensets regularly: Low power voltage can trigger control faults.

Conclusion

A reefer alarm doesn’t always mean disaster — but fast, informed action can save your cargo and reduce costs. By understanding what the most common codes mean, you’ll respond confidently and protect both your product and your cold chain reputation.

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