Has your Thermo King unit been displaying the dreaded Code 627, leaving you stranded and unable to maintain proper refrigeration? Fear not! This enigmatic code often signifies a communication error between the display module and the controller, but with a few simple troubleshooting steps, you can get your unit humming along again and ensure the integrity of your perishable cargo.
To decipher the cause of Code 627, start by verifying the power supply to both the display module and the controller. Ensure that all connections are secure and free of corrosion or damage. If the power supply appears stable, proceed to check the communication cables between the two components. Inspect the cables for any breaks, shorts, or loose connections. Replacing faulty cables is a relatively straightforward procedure, and if that doesn’t resolve the issue, it’s time to delve deeper into the unit’s inner workings.
The next step involves examining the display module itself. If the display is malfunctioning or has lost its programming, it may be transmitting incorrect or incomplete information to the controller. Resetting the display module can often resolve communication issues. Simply disconnect the power supply to the unit, wait a few minutes, and then reconnect it. If the display module still fails to function properly, it may need to be replaced.
Identifying the Thermo King Code 627
Thermo King Code 627, “Lube oil filter clogged or bypass valve stuck open,” indicates an issue with the refrigeration system’s lubricant circuit. This code can trigger when the oil filter becomes clogged with debris or when the bypass valve malfunctions, allowing unfiltered oil to enter the system. The oil filter’s purpose is to remove contaminants from the oil, ensuring the proper lubrication of the compressor and other refrigeration components. A clogged filter can restrict oil flow, leading to insufficient lubrication and potential damage to the compressor. Furthermore, a stuck-open bypass valve allows unfiltered oil to bypass the filter, compromising the oil’s cleanliness and increasing the risk of component wear.
To identify Code 627, observe the following symptoms:
| Symptoms |
|---|
| Reduced cooling performance |
| Increased compressor noise |
| Oil leaks or seepage |
If Code 627 appears on the display panel, it’s crucial to address the issue promptly to prevent further damage. The following section provides guidance on troubleshooting and resolving this code.
Common Causes of Code 627
1. Low Refrigerant Level
One of the most common causes of Code 627 is a low refrigerant level. The refrigerant is responsible for absorbing heat from the unit’s evaporator and releasing it into the atmosphere. If the refrigerant level is too low, the unit will not be able to cool effectively, and the temperature inside the unit will rise.
2. Faulty Temperature Sensor
The temperature sensor is responsible for monitoring the temperature inside the unit. If the temperature sensor is not functioning properly, it may provide inaccurate information to the controller, causing the unit to operate improperly.
There are several reasons why the temperature sensor may malfunction, including:
- Physical damage to the sensor or its components
- Electrical problems, such as a short or open circuit
- The sensor being located in an incorrect position, such as too close to a heat source
3. Compressor Failure
The compressor is the heart of the refrigeration system. It is responsible for compressing the refrigerant and circulating it throughout the system. If the compressor fails, the unit will not be able to cool effectively, and the temperature inside the unit will rise.
| Error Code | Possible Cause |
|---|---|
| 627 | Low refrigerant level |
| Faulty temperature sensor | |
| Compressor failure |
Troubleshooting the Fuel System
Code 627 on a Thermo King unit indicates a fuel system issue. Here are the steps to diagnose and fix the problem:
Check the Fuel Filter
The fuel filter may be clogged, restricting fuel flow. Replace the filter as necessary.
Inspect the Fuel Lines
Inspect the fuel lines for any leaks, cracks, or kinks. Replace any damaged lines.
Check the Fuel Pump
The fuel pump may be failing to deliver enough fuel to the engine. Use a fuel pressure gauge to test the pump’s output. If the pressure is below specifications, replace the pump.
Check the Fuel Injectors
The fuel injectors may be clogged or malfunctioning, preventing proper fuel flow into the engine. Remove and clean the injectors, or replace them if necessary.
Check the Fuel Rail Pressure Sensor
The fuel rail pressure sensor monitors the pressure in the fuel rail. If the sensor fails, the engine may not receive the correct amount of fuel. Test the sensor and replace it if necessary.
Inspecting the Electrical Connections
Thermo King code 627 indicates an issue with the electrical connections within the unit. To fix this code, follow these steps:
1. Check the Battery
Ensure that the battery is properly connected and has sufficient charge. Clean the battery terminals if necessary.
2. Inspect the Wiring Harness
Inspect the wiring harness for any loose connections, damage, or corrosion. Tighten any loose connections and repair or replace damaged wires.
3. Check the Control Module Connections
Locate the control module and check all electrical connections. Ensure that the connectors are securely fastened and free of corrosion or damage.
4. Inspect the Power Connections
Verify that the power connections to the unit are secure and correctly wired. Check the following:
| Component | Check |
|---|---|
| Battery cables | Tighten connections; clean and coat terminals with anti-corrosion spray |
| Generator connections | Tighten connections; inspect for damage or corrosion |
| Starter motor connections | Tighten connections; inspect for damage or corrosion |
| Ground connections | Clean and tighten connections; ensure good contact with the chassis |
| Fuse panel | Check for blown fuses; replace as necessary |
Checking the Refrigerant Charge
Insufficient refrigerant charge is a common cause of Code 627. To check if the system is low on refrigerant:
1. Verify the Refrigerant Sight Glass
Locate the refrigerant sight glass on the suction line. Inspect the glass for the presence of liquid refrigerant with bubbles. If there are no bubbles, or if the sight glass is cloudy, the system may be low on refrigerant.
2. Check the Low-Pressure Gauge
Connect a low-pressure gauge to the system. Start the unit and observe the gauge reading. The normal low-pressure range for a Thermo King refrigeration system is between 15 and 25 psi. A low pressure below 10 psi indicates a possible refrigerant leak.
3. Inspect the Suction Line
Feel the suction line after running the system for several minutes. The suction line should be cool to the touch. If the suction line is warm, it suggests a lack of refrigerant.
4. Listen for Unusual Sounds
Listen for any abnormal sounds coming from the system when it’s running. A high-pitched squealing or hissing sound can indicate a refrigerant leak.
5. Use an Electronic Refrigerant Detector
An electronic refrigerant detector is the most accurate way to pinpoint a refrigerant leak. Follow the manufacturer’s instructions for using the detector to identify any leaks in the system. The detector will emit a signal when it detects refrigerant. Pay particular attention to the joints, fittings, and pipes where leaks are most likely to occur.
| Refrigerant Level | Sight Glass | Low-Pressure Gauge (psi) |
|---|---|---|
| Normal | Visible liquid with bubbles | 15-25 |
| Low | Cloudy or no liquid | Below 10 |
Verifying the Fan Operation
Verifying the fan’s operation is a crucial step in troubleshooting Thermo King Code 627. The fan is responsible for circulating air through the evaporator and condenser coils, ensuring proper cooling and heat exchange. Here’s a step-by-step guide to check the fan’s operation:
1. Access the Fan Unit
Locate the fan unit within the refrigeration system. It’s usually situated at the rear or bottom of the unit.
2. Turn On the Unit
Power up the refrigeration unit and allow it to run for a few minutes.
3. Listen for Fan Operation
Stand close to the fan unit and listen attentively for any sound of operation. A healthy fan should produce a faint whirring or humming noise.
4. Inspect the Fan Blades
Visually inspect the fan blades through the access panel or grille. Make sure they’re spinning freely without any obstructions or damage.
5. Check Fan Wiring
Examine the wiring harness connecting the fan to the unit’s electrical system. Ensure all connections are secure and free of corrosion or damage.
6. Measure Fan Speed
Using a tachometer or anemometer, measure the fan’s speed. Compare the readings to the manufacturer’s specifications provided in the unit’s manual or service bulletin. If the fan speed is significantly lower than the specified range, it may be underperforming or obstructed.
Cleaning the Condenser
The condenser is a crucial component of the refrigeration system, and keeping it clean is vital for optimal performance. Accumulated dirt and debris can impede the condenser’s ability to release heat effectively, leading to reduced cooling capacity and increased energy consumption.
To clean the condenser, follow these thorough steps:
1. Gather Necessary Tools and Materials
- Screwdriver
- Vacuum cleaner with a brush attachment
- Compressed air can (optional)
2. Turn Off the Unit
Ensure the unit is powered down to prevent any electrical hazards.
3. Remove the Access Panel
Locate and remove the access panel to expose the condenser coils.
4. Vacuum the Condenser Coils
Use a vacuum cleaner with a brush attachment to gently remove dirt and debris from the coils. Avoid using excessive force to prevent damage.
5. Rinse the Condenser Coils (Optional)
If the condenser coils are especially dirty, consider rinsing them with a gentle stream of water. Allow them to dry completely before reassembling the unit.
6. Vacuum the Fan Blades
Clean the fan blades that help circulate air through the condenser. Remove any accumulated dust or dirt to ensure optimal airflow.
7. Inspect for Damage or Corrosion
Thoroughly examine the condenser coils, fan blades, and wiring for any signs of damage or corrosion. If any issues are found, contact a qualified technician for repairs or replacement.
| Step | Action |
|---|---|
| 1 | Turn off the unit |
| 2 | Remove access panel |
| 3 | Vacuum condenser coils |
| 4 | Rinse coils (optional) |
| 5 | Vacuum fan blades |
| 6 | Inspect for damage |
Resetting the Code
To reset code 627, follow these steps:
- Locate the wiring harness on the back of the unit.
- Disconnect the wiring harness from the unit.
- Wait 10 seconds.
- Reconnect the wiring harness to the unit.
- Start the unit.
- The code 627 should now be reset.
Additional Information:
If you are unable to reset the code 627 using the steps above, you may need to contact a qualified technician. There may be an underlying issue that is causing the code to appear.
The table below provides additional information about code 627:
| Code | Description |
|---|---|
| 627 | Control circuit voltage out of range |
Advanced Troubleshooting Techniques
1. Check the evaporator coil
The evaporator coil is located in the refrigerated compartment of the unit. It can become iced over, which will restrict airflow and cause the unit to overheat. Cleaning the coil with a soft brush or compressed air can solve this problem.
2. Check the condenser coil
The condenser coil is located on the back or bottom of the unit. It can become clogged with dirt or debris, which will restrict airflow and cause the unit to overheat. Cleaning the coil with a soft brush or vacuum cleaner can solve this problem.
3. Check the fan motor
The fan motor circulates air over the evaporator coil and condenser coil. If the motor fails, the unit will not be able to cool or heat properly. Replacing the motor can solve this problem.
4. Check the thermostat
The thermostat controls the temperature of the refrigerated compartment. If the thermostat fails, the unit may not be able to maintain the desired temperature. Replacing the thermostat can solve this problem.
5. Check the defrost timer
The defrost timer controls the defrost cycle. If the timer malfunctions, the unit may not be able to defrost properly. Replacing the timer can solve this problem.
6. Check the defrost heater
The defrost heater melts ice and frost from the evaporator coil during the defrost cycle. If the heater fails, the unit may not be able to defrost properly. Replacing the heater can solve this problem.
7. Check the thermistor
The thermistor is a temperature sensor that measures the temperature of the refrigerated compartment. If the thermistor fails, the unit may not be able to maintain the desired temperature. Replacing the thermistor can solve this problem.
8. Check the main control board
The main control board is the brains of the unit. It controls all of the other components. If the board fails, the unit will not be able to operate. Replacing the board can solve this problem.
9. Contact a qualified technician
If you have tried all of the above troubleshooting techniques and the unit is still not working properly, you should contact a qualified technician. The technician will be able to diagnose the problem and repair the unit.
Professional Repair Recommendations
Troubleshooting code 627 on a Thermo King refrigeration unit requires a systematic approach. Here are some professional repair recommendations to address this issue effectively:
1. Check Ambient Temperature Sensor
Verify if the ambient temperature sensor is functioning properly. This sensor measures the outside temperature and provides input to the control unit. A faulty sensor can lead to incorrect temperature readings and trigger code 627.
2. Inspect Evaporator Coils
Inspect the evaporator coils for frost or ice buildup. Excessive frost can restrict airflow and cause the unit to overheat, resulting in code 627. Defrost the coils or replace them if necessary.
3. Clean Condenser Coils
Dirt and debris can accumulate on the condenser coils, reducing heat transfer efficiency. Clean the coils using a soft brush or a vacuum cleaner to ensure proper airflow.
4. Check Refrigerant Level
The refrigerant level should be within the specified range. Low refrigerant can cause reduced cooling capacity and trigger code 627. Have a qualified technician check and replenish the refrigerant if necessary.
5. Inspect Fan Motor
The fan motor is responsible for circulating air through the unit. A faulty fan motor can lead to inadequate airflow and overheating, causing code 627. Check the motor for any obstructions or damage.
6. Check Switches and Wiring
Inspect all switches and wiring for any loose connections, shorts, or damage. Faulty switches or wiring can disrupt the control system and trigger code 627.
7. Inspect for Leaks
Check the system thoroughly for any leaks in the refrigerant lines, evaporator, or condenser. Leaks can lead to refrigerant loss and reduced cooling capacity, resulting in code 627.
8. Reset Control Unit
In some cases, resetting the control unit can resolve the issue. Follow the manufacturer’s instructions to reset the unit and observe if code 627 persists.
9. Monitor Voltage
The electrical system should provide the correct voltage to the refrigeration unit. Fluctuating voltage can affect the performance of various components and trigger code 627. Ensure that the voltage is stable and within the specified range.
10. Compressor Diagnostics
If the above steps do not resolve the issue, it is recommended to perform in-depth compressor diagnostics. This involves checking the compressor’s mechanical operation, electrical parameters, and internal components. A qualified technician can accurately diagnose and repair the compressor to address code 627 and restore optimal unit performance.
Thermo King Code 627 How To Fix
Thermo King Code 627 is a fault code that indicates a problem with the unit’s evaporator fan motor. The evaporator fan motor is responsible for circulating air over the evaporator coil, which cools the air inside the unit. If the evaporator fan motor fails, the unit will not be able to cool the air properly.
There are several things that can cause Thermo King Code 627, including:
- A faulty evaporator fan motor
- A problem with the wiring to the evaporator fan motor
- A problem with the control board
- A problem with the power supply
How to fix Thermo King Code 627
To fix Thermo King Code 627, you will need to troubleshoot the problem and replace any faulty components. Here are the steps on how to troubleshoot and fix Thermo King Code 627:
- Check the evaporator fan motor. Make sure that the motor is not seized or damaged. If the motor is damaged, it will need to be replaced.
- Check the wiring to the evaporator fan motor. Make sure that the wires are not damaged or loose. If the wiring is damaged, it will need to be repaired or replaced.
- Check the control board. The control board is responsible for sending power to the evaporator fan motor. If the control board is damaged, it will need to be replaced.
- Check the power supply. Make sure that the unit is receiving power. If the unit is not receiving power, check the circuit breaker or fuse.
People also ask about Thermo King Code 627 How To Fix
What are the symptoms of Thermo King Code 627?
The symptoms of Thermo King Code 627 include:
- The unit is not cooling properly.
- The evaporator coil is freezing up.
- The unit is making a loud noise.
How much does it cost to fix Thermo King Code 627?
The cost to fix Thermo King Code 627 will vary depending on the cause of the problem. If the evaporator fan motor is faulty, the cost to replace it will be around $200. If the wiring to the evaporator fan motor is damaged, the cost to repair it will be around $100. If the control board is damaged, the cost to replace it will be around $300. If the power supply is faulty, the cost to repair it will vary depending on the problem.
How can I prevent Thermo King Code 627 from happening again?
There are several things you can do to prevent Thermo King Code 627 from happening again, including:
- Keep the unit clean. A dirty unit is more likely to experience problems.
- Inspect the unit regularly. Look for any signs of damage or wear and tear.
- Service the unit regularly. A qualified technician can inspect the unit and make sure that it is operating properly.
