Evaporator / Condenser Fan Problems

Low Refrigerant Level

Lack of refrigerant in the system's refrigeration circuit.

Alarm 10 – Supply Air Temperature Sensor (SATS) Out of Range

Carrier Transicold alarm AL10 (Alarm Code 10) means the Advance microprocessor has detected the Supply Air Temperature Sensor (SATS/STS) reading is out of range, open, or shorted. The SATS lives in the discharge airstream after the evaporator on Vector, X4, X2 and Supra reefer units and is the primary control sensor when 'Supply' is selected. When AL10 latches, the controller falls back to the Return Air Sensor and box temperature control becomes unstable — a frequent cause of load-quality claims.

High Coolant Temp

Engine temperature has exceeded the maximum safe operating limit.

High Discharge Pressure

Refrigerant discharge pressure exceeded the safety limit.

High A/C Amps

High electrical current detected in AC system components.

Alarm 17 – High Compressor Discharge Temperature (CDT)

Carrier Transicold alarm code 17 (AL17) triggers when Compressor Discharge Temperature (CDT) climbs above the safety threshold — typically 310°F (154°C) on Vector, X4, X2 and Supra reefer units. The Advance controller shuts the unit down to protect the compressor from thermal breakdown of oil, valve plate damage, and burned windings. AL17 almost always points at a refrigerant-side or airflow problem, not the compressor itself.

Low Refrigerant Press

Refrigerant pressure too low for safe operation.

Low Suction Superheat

Low suction superheat, risk of liquid floodback to compressor.

A/C Current Over Limit

AC current consumption exceeded pre-set limits.

Failed To Start – Manual

Failure to start the unit in manual mode.

Check Starter Circuit

Anomaly detected in the starter motor electrical circuit.

Check Coolant Temp

Engine temperature is not rising or is out of expected range.

Box Temp Out of Range

The temperature inside the box is outside the established tolerance range relative to the setpoint.

Defrost Not Complete

The defrost cycle has exceeded the maximum allowed time without completing correctly.

Check Evaporator Air Flow

The system has detected a significant restriction in airflow through the evaporator.

C2 Box Temp Out of Range

Second compartment (C2) temperature is outside allowable limits.

Bad F2 or F3 Fuse

Failure in fuses F2 or F3 which control vital accessory power circuits.

AC Phase Reversed

External AC power phase is reversed, which can damage motors.

Compressor Motor Overload

The compressor motor overload relay has tripped due to excessive current.

Condenser Motor Overheated

The condenser fan motor thermal sensor reports excessive temperature.

Evap Motor Overheated

The evaporator fan motor is operating above its safe temperature threshold.

Check CDCON Relay Coil

Failure in the CDCON relay coil (Condenser Fan).

Check High Temperature Thermostat

Activation of the high temperature thermostat (Overheat protection).

Overload/Ground Fault

Electrical overload or ground fault detected in the system.

C2 Evap Motor Overheated

Overheating detected in the Compartment 2 evaporator motor.

C3 Evap Motor Overheated

Overheating detected in the Compartment 3 evaporator motor.

Check 3LSV Circuit

Issue in the Liquid Line Solenoid Valve 3 (3LSV) circuit.

Check 1EVCON Relay Coil

Fault in the evaporator motor contactor 1 (1EVCON).

Check 2EVCON Relay Coil

Fault in the evaporator motor contactor 2 (2EVCON).

Check 3EVCON Relay Coil

Fault in the evaporator motor contactor 3 (3EVCON).

Low/Unbalanced A/C Amps

Low or unbalanced AC current amperage detected at the generator.

Check Evap Temp Sensor

Failure detected in the evaporator coil temperature sensor.

C2 Check Supply Air Sensor

Supply air sensor error for compartment 2 (C2).

C3 Check Return Air Sensor

Return air sensor error for compartment 3 (C3).

C3 Check Defrost Sensor

Defrost sensor error for compartment 3 (C3).

Check SV3 Circuit

Failure in solenoid valve 3 (SV3) circuit.

Check Evap Superheat

Evaporator superheat is outside design limits.

Check Suction Mod Valve

Failure in the Suction Modulation Valve (SMV).

C2 Check Evap Fan Motor

Fault detected in the compartment 2 evaporator fan motor.

C3 Check Evap Fan Motor

Fault detected during Pretrip in the compartment 3 evaporator fan motor.

Check Evap Outlet Temp

The evaporator outlet temperature sensor does not respond correctly during tests.

Check Evap Fan Motor

General evaporator fan motor error detected during self-inspection.

Check Condenser Fan Motor

Fault in the condenser fan motor, compromising heat dissipation.

High Discharge Pressure

Dangerously high discharge pressure; risk of high pressure cutout.

Check Defrost Term 2 Sensor

Failure in the evaporator 2 defrost termination sensor.

Check Condenser Fan Circuit

Error in the control or power circuit of the condenser fans.

C3 Check Defrost Sensor

Failure in the compartment 3 defrost sensor.

Check Damper – Not Open

The defrost damper is stuck in the closed position or is not opening properly.

Check Damper – Not Closing

The defrost damper does not close properly, preventing proper airflow during refrigeration.

Standby Maintenance Due

The scheduled interval for electric motor (Standby) service has expired.

Suct/Evap Calibrate Error

Calibration error in the suction or evaporator pressure sensors.

Motor Overload 1

Overload detected in the electric motor or fan motor 1.

Check CDCON Relay Coil Two

Failure in coil 2 of the condenser contactor relay (CDCON).

Cond. Motor 2 Overheated

Internal overheat protection for condenser motor 2 activated.

C2 Chk Evap Temp Sensor

Indicates a problem with the evaporator temperature sensor in compartment 2.

C2 Chk Evap Outlet Temp

Error in compartment 2 evaporator outlet temperature detected during Pre-Trip.

C3 Chk Evap Outlet Temp

Error in compartment 3 evaporator outlet temperature detected during Pre-Trip.

Check Condenser Fan 2 Circuit

Failure in the condenser fan number 2 circuit during self-check.

C2 Chk Evap1 Superheat

Superheat out of range in evaporator 1 of compartment 2.

C2 Chk Evap2 Superheat

Superheat out of range in evaporator 2 of compartment 2.

C3 Chk Evap1 Superheat

Superheat out of range in evaporator 1 of compartment 3.

C3 Chk Evap2 Superheat

Superheat out of range in evaporator 2 of compartment 3.

No Comm From Micro to STP1

Communication failure between the microprocessor and the stepper motor module 1 (STP1).

Over Current STP1

Overcurrent detected in the stepper motor 1 (STP1) circuit.

No Comm From Micro to STP2

Communication failure between the microprocessor and the stepper motor module 2 (STP2).

Over Current STP2

Overcurrent detected in the stepper motor 2 (STP2) circuit.

No Comm From Micro to STP3

Communication failure between the microprocessor and stepper motor module 3 (STP3).

Over Current STP3

Overcurrent detected in the stepper motor 3 (STP3) circuit.

No Comm From Micro to STP4

Communication failure between the microprocessor and stepper motor module 4 (STP4).

Over Current STP4

Overcurrent detected in the stepper motor 4 (STP4) circuit.

Engine Over Heat ENCU

Engine has exceeded the maximum safety temperature limit configured by the ENCU.

Water Temp Low ENCU

Coolant temperature too low; engine failing to reach operating temperature.

Check Evaporator Coil Sensor (Zone)

The microprocessor has detected a failure or out-of-range reading in the evaporator coil sensor.

Check (Control) Discharge Air Sensor (Zone)

Failure of the discharge air sensor, which measures the air leaving the evaporator toward the cargo.

High Evaporator Temperature (Zone)

An excessively high evaporator temperature has been detected.

High Discharge Pressure (or Temperature)

The compressor discharge pressure or temperature has exceeded safety limits.

Sensor Check (Zone)

The microprocessor has detected an unusual discrepancy between temperature sensors.

Engine Failed to Crank

The starter motor does not turn or the engine fails to rotate for ignition.

Check Refrigeration Capacity (Zone)

Refrigeration capacity is lower than expected for the current setpoint.

Vapor Motor RPM High (CR)

Steam motor or electric compressor revolutions exceed the safety limit.

Defrost Damper Stuck Closed (Zone)

The evaporator damper has become stuck in the closed position.

Refrigeration Capacity Low (Zone)

The unit or zone is not reaching the expected cooling capacity and has been stopped for safety.

Electric Motor Failed to Run

The backup electric motor does not start when standby mode operation is required.

Check Engine Coolant Temp

Engine coolant temperature is unusually high or the sensor is failing.

Check Air Flow (Zone)

Restriction detected in evaporator airflow in the indicated zone.

Check Evaporator Fan Low Speed (Zone)

Failure detected in the evaporator fans' low-speed circuit.

Check Evaporator Fan High Speed (Zone)

A fault was detected in the high-speed circuit of the evaporator fans.

Engine or Vapor Motor Stopped

The diesel engine or electric motor stopped unexpectedly due to mechanical or fuel reasons.

Abnormal Temperature Differential (Zone)

Abnormal temperature differential detected in a specific zone (evaporator).

ETV Fault – Electronic Throttling Valve Circuit (Code 89)

Thermo King alarm code 89 indicates a failure in the Electronic Throttling Valve (ETV) control circuit. The ETV is a stepper-motor modulating valve in the suction line that regulates suction pressure and compressor loading on Thermo King SB-, SLXi, SLXe, SLX, SLX Whisper, T-Series, Precedent and TriPac reefer units. When the microprocessor cannot drive or read the ETV stepper coils correctly, it logs Code 89 and forces the unit into a protective mode — often unable to hold setpoint or pull down.

Low Compressor Suction Pressure

Dangerously low compressor suction pressure detected.

Failed Remote Return Air Sensor (CR)

Remote return air sensor failure preventing accurate zone temperature reading.

High Compressor Pressure Ratio

Excessive pressure ratio detected between compressor suction and discharge, risking mechanical integrity.

Heater Fan Failure (CR)

Fault detected in the heater fan motor or circuit.

Controlling on Evap Coil Outlet Temp (CR)

Unit is controlling temperature based on evaporator outlet due to a primary sensor failure.

Low Evaporator Coil Temperature (CR)

Evaporator coil temperature is dangerously low, which may lead to icing or freezing.

Check Remote Fan Speed (Zone)

The controller cannot detect or maintain the required speed for the remote zone fans.

Check Condenser Inlet Sol Circuit

Error detected in the condenser inlet solenoid valve circuit.

Check Suction Line Sol Circuit (Zone)

Failure in the suction line solenoid valve circuit for a specific zone.

Check Remote Fans (Zone)

The remote zone fans are not operating as required.

Check High Pressure Cut Out Switch

Fault in the High Pressure Cut Out (HPCO) switch or its circuit.

Auto Switch from Diesel to Electric

The unit has automatically switched from diesel operation to electric motor operation.

Auto Switch from Electric to Diesel

The unit has automatically switched from electric motor to diesel operation.

Check Diesel/Electric Circuit

Error when attempting to switch between diesel and electric mode or vice versa.

Check Evap Coil Inlet Temp Sensor (CR)

Failure in the evaporator coil inlet temperature sensor (CR).

Check Evap Coil Outlet Temp Sensor (CR)

Failure in the evaporator coil outlet temperature sensor (CR).

Check Damper Motor Heater Output

Fault in the heater circuit for the defrost damper motor.

Check Remote Drain Hose Heater Output (Zone)

Error in the remote drain hose heater output in a specific zone.

Check Multi-Temp Fan Speed Control Output (Zone)

Error in the speed control of the multi-temperature evaporator fans.

Sensor Out of Range Low (DAS and HMI) (Zone)

A sensor (air, evaporator) is reporting a measurement below the minimum limit.

Check Electronic Expansion Valve (CR)

Failure in the electronic expansion valve (EEV) circuit or mechanism.

Check Evaporator Pressure Sensor (CR)

The evaporator pressure sensor is sending signals that are out of range.

Check Host Evaporator Blower Low Speed

Problem detected in the low speed of the main evaporator blower.

Check Host Evaporator Blower High Speed

Problem detected in the high-speed operation of the host evaporator blower.

Check Roadside Condenser Fan Motor Speed Circuit

Fault in the speed control circuit of the roadside condenser fan motor.

Check Curbside Condenser Fan Motor Speed Circuit

Fault in the speed control circuit of the curbside condenser fan motor.

High Compressor Suction Pressure (Scroll Only)

Excessively high suction pressure detected in Scroll-type compressors.

Generator Ground Fault

Current leakage to ground detected in the generator circuit.

Battery Charger External/Environmental Fault

Battery charger failure caused by external or environmental factors.

Generator Operational Limit Output Current

The generator has reached or exceeded its operating output current limit.