Thermo King Apu Troubleshooting Guide: Mastering the Art of Diagnosing and Fixing Apu Issues

When troubleshooting a Thermo King APU, refer to the user manual for specific instructions. Thermo King APU troubleshooting guides provide step-by-step solutions for common issues, ensuring smooth operation and optimal performance.

If you encounter problems such as abnormal noises, loss of power, or malfunctioning controls, follow the troubleshooting guide to identify and resolve the issue efficiently. Proper maintenance and troubleshooting can extend the lifespan of your Thermo King APU and prevent costly repairs.

With the correct troubleshooting procedures, you can quickly diagnose and fix issues, minimizing downtime and maximizing productivity. Understanding the troubleshooting guide can help you address potential problems proactively, ensuring your Thermo King APU operates reliably.


Common Apu Issues

Electrical Problems

Electrical problems are one of the most common issues with Thermo King APU systems, leading to various malfunctions. Flickering lights, blown fuses, and faulty wiring can cause the APU to stop working altogether. A thorough inspection of the electrical components and connections is necessary to identify and rectify these issues.

Cooling System Malfunctions

The cooling system is vital for proper APU function, and issues in this area can lead to overheating and inefficient cooling. Clogged filters, leaks, or malfunctioning fans can disrupt the cooling process, impacting the APU’s overall performance. Regular maintenance and cleaning are crucial to ensuring the proper functioning of the cooling system.

Fuel And Emission Related Problems

Issues related to fuel delivery and emission control can also affect the APU’s performance. Clogged fuel filters, leaking fuel lines, and excessive exhaust emissions are common problems that require immediate attention. Regularly inspecting and maintaining the fuel and emission systems can prevent these issues from escalating.

Diagnostic Tools And Techniques

When it comes to troubleshooting a Thermo King APU, having the right diagnostic tools and techniques is crucial.

Understanding Thermo King Apu Error Codes

Thermo King APU error codes can provide valuable insight into potential issues with the unit.

Using Multimeter For Electrical Diagnosis

A multimeter is a handy tool to check electrical components for any faults or irregularities.

Pressure Testing For Cooling System Issues

Pressure testing can help identify leaks or malfunctions within the cooling system of the APU.

Electrical Troubleshooting

In order to ensure the smooth operation of your Thermo King Auxiliary Power Unit (APU), it is important to regularly perform electrical troubleshooting. This process involves inspecting and testing various components related to the electrical system. In this guide, we will cover three key areas of electrical troubleshooting: battery and alternator checks, wiring inspection and repair, and solenoid and relay testing. By following these steps, you can identify and resolve any electrical issues that may arise, helping to keep your Thermo King APU running at optimal performance.

Battery And Alternator Checks

The battery and alternator are crucial components of the APU electrical system. To determine their condition, follow these steps:

  1. Step 1: Battery Voltage Check

    Using a multimeter, measure the voltage of the battery while the APU is turned off. It should read around 12.6 volts for a fully charged battery. If the reading is significantly lower, the battery may need to be recharged or replaced.

  2. Step 2: Alternator Output Check

    Start the APU and run it at a high idle. Measure the voltage at the battery terminals using the multimeter. It should read around 13.8 to 14.4 volts. If the reading is lower, there may be an issue with the alternator or its connections.

Wiring Inspection And Repair

Proper wiring is essential for the electrical system to function correctly. Follow these steps to inspect and repair any faulty wiring:

  1. Step 1: Visual Inspection

    Thoroughly examine the wiring harness for any signs of damage, such as frayed or exposed wires. Additionally, check for loose connections or corrosion on terminals.

  2. Step 2: Continuity Check

    Using a multimeter set to the continuity test mode, check the integrity of the wiring connections. Touch the multimeter probes to each end of the wire or connection to ensure there is proper continuity. If there is no continuity, the wire may need to be repaired or replaced.

Solenoid And Relay Testing

Solenoids and relays play a crucial role in controlling various electrical functions within the Thermo King APU. Here’s how to test their functionality:

  1. Step 1: Solenoid Function Test

    Refer to the APU’s manual to identify the solenoids and their respective functions. Energize each solenoid individually using a power source and ensure that it operates as expected.

  2. Step 2: Relay Operation Test

    Using a multimeter set to the diode test mode, test the relays for proper operation. Apply voltage across the relay coil terminals and listen for a clicking sound, indicating that the relay is functioning correctly. Additionally, check for continuity across the relay’s switch terminals.

Cooling System Diagnosis

Get expert guidance on diagnosing the cooling system in your Thermo King APUs with this comprehensive troubleshooting guide. Discover effective methods for identifying and resolving issues to ensure optimal performance and reliability. Keep your APUs running smoothly with the knowledge and insights provided in this comprehensive resource.

The cooling system in a Thermo King APU plays a crucial role in maintaining optimal temperatures for refrigerated cargo and preventing any damage to the unit. It is essential to regularly diagnose and troubleshoot the cooling system to ensure its proper functionality and prevent any potential breakdowns while on the road. This section will guide you through the key steps in conducting a cooling system diagnosis for your Thermo King APU.

Checking Refrigerant Levels

Proper refrigerant levels are essential for the cooling system to function efficiently. Insufficient refrigerant can result in inadequate cooling and potentially damage the APU. Here’s how you can check the refrigerant levels:

  1. Locate the sight glass on the liquid line. This glass provides a visual indication of the refrigerant levels.
  2. If the sight glass appears cloudy or shows bubbles, it may indicate a low refrigerant level. In such cases, it is recommended to consult a professional technician for further examination and potential recharging.
  3. Ensure all valves and connections are secure and properly sealed to prevent any leaks.

Examining Fans And Belts

The fans and belts in the cooling system play a crucial role in maintaining proper airflow and preventing overheating. Regular examination of these components is essential to identify any signs of damage or wear. Here’s how you can examine the fans and belts:

  • Visually inspect the fans for any signs of damage such as cracks or bent blades. Replace any damaged fans immediately to prevent potential breakdowns.
  • Check the tension of the belts. They should have the right amount of tension to ensure proper rotation and prevent slipping. Replace worn-out or loose belts as needed.
  • Ensure the fans are clean and free from any debris that could hinder their performance. Use compressed air or a soft brush to remove any dirt or obstructions.

Identifying Leaks

Leaking refrigerant can lead to a loss in cooling capacity and potentially damage other components of the APU. It is crucial to identify and address any leaks promptly. Here’s how you can identify leaks in the cooling system:

  1. Inspect all refrigerant lines and connections for any signs of leakage, such as oil stains or wet spots.
  2. Use a leak detection solution or UV dye to identify any hidden leaks that may not be immediately visible.
  3. If you detect any leaks, it is recommended to contact a professional technician to repair and recharge the refrigerant system.

Fuel And Emission Troubleshooting

Fuel System Inspection

When dealing with Thermo King APU fuel issues, it’s crucial to begin with a thorough fuel system inspection. This involves checking for leaks, blockages, or damaged components.

Emission Control Component Examination

Ensuring proper functionality of emission control components is essential for maintaining compliance. Conduct a meticulous examination to identify any issues affecting emissions.

Apu Regeneration Problems

One common concern is APU regeneration problems, which can impact emissions. Keep an eye out for any irregularities and address them promptly to maintain optimal performance.

Preventive Maintenance

One of the most effective ways to ensure the efficient performance of your Thermo King APUs is through preventive maintenance. By proactively identifying and addressing potential issues, you can minimize costly downtime and prolong the lifespan of your APU. Here are the key aspects of preventive maintenance that you should focus on:

Regular Inspections And Servicing

Regular inspections and servicing are essential for identifying and addressing potential issues before they escalate into major problems. Perform visual inspections of the APU components to check for any signs of wear or damage. Additionally, adhere to the manufacturer’s recommended service intervals to replace worn-out parts and ensure optimal performance.

Component Cleaning And Lubrication

Component cleaning and lubrication are crucial for maintaining the efficiency and longevity of your Thermo King APUs. Keep the APU components free from dirt, debris, and corrosion by regularly cleaning them. Proper lubrication of moving parts such as fans, belts, and bearings will reduce friction and wear, extending the lifespan of the APU.

Software Updates And Calibration

Software updates and calibration play a significant role in the performance and efficiency of Thermo King APUs. Ensure that the APU’s software is updated to the latest version to optimize functionality and address any known issues. Additionally, regular calibration of sensors and controls will ensure accurate operation and prevent potential malfunctions.

Frequently Asked Questions Of Thermo King Apu Troubleshooting Guide

What Are The Common Thermo King Apu Issues?

Thermo King APU commonly faces issues like fuel leaks, electrical faults, and cooling system problems. Regular maintenance can help prevent these issues.

How To Troubleshoot Thermo King Apu Not Starting?

Check the fuel level, battery connections, and fuses. Ensure proper airflow and inspect for any visible damages. Follow manufacturer guidelines for troubleshooting steps.

Why Is My Thermo King Apu Overheating?

Thermo King APU overheating can be due to a malfunctioning fan, low coolant levels, or a faulty thermostat. Address these issues promptly to avoid damage.


Boost your Thermo King APUs with our troubleshooting guide for efficient operations. Keep your fleet on the road with these easy-to-follow solutions. Maximize your APU’s performance and save on unnecessary maintenance costs. Empower yourself with the knowledge to tackle any issues swiftly and effectively.

Your Thermo King APU is in good hands with these troubleshooting tips.

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