PTI Test for Refrigerated Containers: Why You Should Never Skip It Before Shipment

Let’s start with the essentials.

A PTI (Pre-Trip Inspection) is a comprehensive technical inspection of a refrigerated (reefer) container before it is loaded with cargo. It is not a quick visual check but a standardized diagnostic procedure that typically takes several hours and evaluates every critical system of the refrigeration unit.

Without a PTI, a refrigeration unit that appears to be functioning normally may fail during transit—resulting in spoiled cargo, financial losses, and liability for the carrier or container operator.

Below, we’ll explain what a PTI includes, why it’s important, and how it protects everyone involved in the cold chain.

Common Problems Found in Reefer Containers

When a refrigerated container returns from a voyage or has been stored for an extended period, its technical condition is often unknown.

Typical hidden issues include:

● Refrigeration system fault codes stored in the controller

● Partial refrigerant loss

● Temperature sensors that have drifted out of calibration

● Electrical faults

● Air circulation problems

The refrigeration unit may still start and produce cold air, yet be operating close to failure.

A PTI removes this uncertainty.

During the inspection, the refrigeration unit is tested under simulated operating conditions, including:

● Cooling mode

● Heating mode

● Temperature setpoint changes

● Ventilation performance

● System tightness and leak checks

If hidden defects exist, they are discovered at the terminal—before cargo is loaded—not during the journey.

What Does a PTI Test Check?

The PTI follows a strict inspection sequence specified by the equipment manufacturer.

A diagnostic computer connects directly to the refrigeration controller and tests every major component.

The inspection includes:

● Compressor performance

● Expansion valve operation

● Refrigerant pressure

● Operating mode switching

● Compressor crankcase heater

● Evaporator fan operation

● Condenser fan operation

● Temperature sensor accuracy

● Electrical wiring integrity

Once testing is complete, the system generates an inspection report indicating either:

● PTI Passed

● Faults Detected

If faults are identified, the report lists the corresponding diagnostic error codes.

The completed PTI report is then provided to the shipper and, when required, to the shipping line.

PTI Error Code Reference

Power Supply and Communication Errors

Error Code	Description	Recommended Action
AL50 / AL051	Power supply interruption detected. The controller recorded an unexpected power loss.	Inspect the power cable and plug. Check controller terminals for corrosion or overheating. If the event occurred only once, repeat the PTI. If recurring, replace the power cable or repair the power supply.
AL51 / AL052	Controller parameter or memory fault.	Restart the controller and update the firmware. If the problem persists, diagnose or replace the control board.
AL10 / AL011	High supply voltage detected.	Check the terminal power supply, transformer, and electrical circuits. If the event was isolated, clear the fault log and repeat the PTI. Persistent voltage spikes require power protection measures.
AL11 / AL012	Low supply voltage detected.	Inspect the electrical supply and connections. If necessary, connect the unit through a voltage stabilizer.

Temperature Sensor Errors

Error Code	Description	Recommended Action
AL20 / AL020	Supply air temperature sensor open circuit or out of range.	Inspect the wiring and connector, replace the sensor if necessary, recalibrate, and repeat the PTI.
AL21 / AL021	Return air temperature sensor fault.	Diagnose wiring, replace the sensor, recalibrate, and repeat the PTI.
AL26 / AL026	Excessive difference between supply and return air temperatures.	Verify calibration using a reference thermometer. Replace faulty sensors if required. If sensors are accurate, inspect airflow and the evaporator for blockage.
AL27 / AL027	Evaporator temperature sensor failure.	Inspect the sensor for mechanical damage, replace if necessary, and verify installation.

Refrigerant and Compressor Errors

Error Code	Description	Recommended Action
AL53 / AL053	Low suction pressure.	Check refrigerant charge, locate and repair leaks, recharge the system, and inspect the expansion valve and filter-drier if pressure remains low.
AL54 / AL054	High discharge pressure.	Clean the condenser, inspect condenser fan operation, flush the heat exchanger, and check for restrictions or a clogged filter-drier.
AL55 / AL055	Compressor failure or overload protection activated.	Inspect the contactor and starting relay, measure winding resistance, replace the compressor if seized, and inspect compressor oil condition.
AL57 / AL057	High-pressure safety shutdown.	Investigate refrigerant overcharge, blocked condenser, or faulty pressure switch. The container must not be loaded until the cause is corrected.

Defrost System Errors

Error Code	Description	Recommended Action
AL60 / AL060	Defrost heater failure.	Inspect heater circuits, electrical connections, and heating elements. Replace defective heaters and verify relay operation.
AL61 / AL061	Defrost cycle exceeded maximum time.	Check for excessive ice buildup, blocked drains, and faulty defrost termination sensors.
AL62 / AL062	Defrost cycle did not start.	Diagnose the control circuit, relay, and controller board.

Ventilation and Airflow Errors

Error Code	Description	Recommended Action
AL70 / AL070	Evaporator fan failure.	Inspect power supply, motors, and fan blades for mechanical obstruction. Replace faulty motors and check protective guards.
AL71 / AL071	Condenser fan failure.	Diagnose the fan motor, replace if necessary, and inspect mounting hardware.
AL72 / AL072	Insufficient airflow.	Clean the evaporator, inspect air passages, and verify cargo loading patterns if the container is loaded. Confirm correct fan rotation.

Controller and Firmware Errors

Error Code	Description	Recommended Action
E001 / EE001	Internal controller memory error.	Restart or reflash the controller. Replace the control board if the fault returns.
E002 / EE002	Communication failure between the controller and display or peripheral module.	Inspect cables and connectors. Replace the display module or cable if required.
E101	Real-time clock error.	Reset and synchronize the controller clock using diagnostic software. Replace the controller battery if necessary.

Booking a PTI Test

A PTI inspection can be requested:

● When placing a refrigerated container into storage, or

● As a standalone service for containers already stored at our terminal.

Testing is normally completed within one business day after the request is confirmed.

PTI pricing is fixed and discussed when the service agreement is signed.

Answers to questions

My reefer passed a PTI in Hamburg a week ago. Do I really need another PTI before loading in Minsk?

If the shipping line or cargo owner accepts a PTI certificate issued within the last 30 days, another inspection may not be mandatory.
However, we strongly recommend performing a new PTI. During transportation, the refrigeration unit may have experienced impacts, vibration, or sensor calibration drift. Spending a few extra hours on a fresh inspection is a small investment compared with the risk of cargo loss—especially for pharmaceuticals or other high-value temperature-controlled goods.

Can you perform the PTI without me being present? I only need the inspection report for the shipping line.

Yes.
This is our standard procedure.
Submit your request through the SKAT system or by email. We’ll move the container to the testing area, connect the refrigeration unit, complete the full inspection cycle, and email you the PTI report.
If no faults are detected, you can simply forward the report to your customer or shipping line.
If any error codes appear, we’ll contact you immediately to discuss the next steps.

The PTI report shows AL55 (compressor failure). My container is scheduled to load tomorrow night. Can the shipment still be saved?

AL55 indicates a serious compressor-related fault.
Repair times depend on the nature of the failure, and some replacement parts may not be immediately available in Belarus.
We’ll assess the unit as quickly as possible and advise you on the expected repair schedule.

I have an older Thermo King unit without a digital display. Can you still perform a PTI?

Yes.
We use diagnostic equipment with adapters compatible with most refrigeration controllers, including many older models.
If the unit is too old to support digital diagnostics, we perform the inspection manually using external measuring instruments.
Shipping lines generally accept this type of inspection report, although specific requirements may vary.
Please let your account manager know the refrigeration unit model in advance.

My PTI report shows a “logged AL26 error.” My customer in China requires a completely clean PTI report. Can the test be repeated?

Yes.
A logged error does not necessarily indicate an active fault.
We first clear the controller’s fault history and repeat the PTI.
If AL26 does not reappear, it was only a historical record and the new report will be clean.
If the error returns, the temperature sensors require inspection or replacement.
Repeating the test is usually much faster than disputing the report with the consignee.

My reefer has only been stored for one month while connected to power. Do I really need a full PTI?

A full PTI typically takes around three hours.
If appropriate for your operational requirements, we can also perform a short PTI, which usually takes approximately one hour.
Our specialists can help determine which inspection level is suitable for your shipment.

What happens if I skip the PTI altogether and load the container anyway?

Skipping a PTI can have serious consequences.
A shipper may refuse to load cargo into a reefer that lacks a valid inspection certificate, or the container may be rejected during inspection at the port of departure.
More importantly, if the refrigeration unit fails during transit and the cargo is damaged, the insurer will almost certainly ask whether a valid PTI was completed before shipment.
Without one, an insurance claim may be denied.
Attempting to save a few hundred dollars on inspection can ultimately result in losses worth hundreds of thousands, which is why experienced carriers and container operators rarely take that risk.