AC In Car Blowing Hot Air : Case study & Solution

AC in Car Blowing Hot Air

Few things are as frustrating as turning on your car’s air conditioning on a hot day only to be met with a blast of warm air. A well-functioning AC system is crucial for comfort, especially during sweltering summers. When the AC in car blowing hot air, it’s not just an inconvenience—it’s a sign that something within the system isn’t working as it should. In this article, we’ll explore the common causes of this issue, how to diagnose it, and the best solutions to get your AC back to cooling as it should.

Common Causes of AC in Car Blowing Hot Air

Refrigerant Issues

One of the most common reasons your car’s AC might be blowing hot air is due to refrigerant problems.

Low Refrigerant Levels: The refrigerant is crucial for cooling the air. Low levels often result from leaks and cause the AC to blow warm air.
Refrigerant Leaks: Leaks can occur in various parts of the AC system, such as the hoses, compressor, or evaporator. Even a small leak can lead to significant refrigerant loss over time.

Component Failures

Several key components must work properly to ensure the AC system functions correctly.

Faulty Compressor: The compressor is the heart of the AC system, circulating the refrigerant. If it fails, the entire system stops working effectively.
Malfunctioning Condenser: The condenser dissipates heat from the refrigerant. If it’s blocked or broken, the refrigerant doesn’t cool down properly.
Defective Evaporator: The evaporator absorbs heat from the car’s interior. A malfunction can prevent the AC from cooling the air.

Electrical Problems

Electrical issues can also cause your AC to blow hot air.

Blown Fuses: Fuses protect the AC system’s electrical components. A blown fuse can disrupt power to the AC system.
Faulty Wiring: Damaged or corroded wiring can interrupt the electrical flow, causing various parts of the AC to malfunction.
Bad AC Control Module: The control module regulates the AC system. A malfunctioning module can cause the system to behave erratically or stop working.

Obstruction in the System

Blockages within the AC system can impede its operation.

Blocked or Clogged Condenser: Debris and dirt can block the condenser, reducing its ability to dissipate heat.
Clogged Air Filters: Dirty air filters can restrict airflow, making it harder for the AC system to cool the air.

Diagnosing the Problem AC in Car Blowing Hot Air

Visual Inspection

Start with a simple visual inspection.

Checking for Visible Leaks: Look for signs of refrigerant leaks, such as oily residue on AC components.
Inspecting AC Components: Check the condition of the compressor, hoses, and other visible parts for any signs of damage.

Using Diagnostic Tools

Sometimes, you’ll need specialized tools to diagnose the problem.

Pressure Gauges: These can help determine if the refrigerant pressure is within the normal range.
Refrigerant Leak Detectors: These devices can help locate small leaks that are not visible to the naked eye.

Professional Diagnosis

For complex issues, professional diagnosis is often necessary.

Importance of Professional Inspection: Trained technicians have the tools and expertise to accurately diagnose and fix AC problems.
What to Expect During a Professional Check-up: Technicians will use various tools to check the refrigerant levels, electrical connections, and the condition of AC components.

Solutions and Repairs AC in Car Blowing Hot Air

Recharging Refrigerant

If low refrigerant levels are the issue, recharging might be the solution.

When and How to Recharge: Recharging involves adding more refrigerant to the system. It’s essential to use the correct type and amount of refrigerant.
DIY vs. Professional Service: While recharging can be a DIY task, professional service ensures it’s done correctly and safely.

Repairing or Replacing Components

Depending on the diagnosis, certain components might need repair or replacement.

Cost and Complexity of Common Repairs: Replacing major components like the compressor or condenser can be costly and complex, often requiring professional service.

Addressing Electrical Issues

Electrical problems require careful troubleshooting.

Troubleshooting Electrical Problems: Identify and fix issues like blown fuses or damaged wiring.
Fixing Fuses and Wiring: Replace blown fuses and repair or replace faulty wiring to restore power to the AC system.

Regular Maintenance

Preventive maintenance can keep your AC system in top shape.

Importance of Regular AC Maintenance: Regular check-ups can prevent major issues from developing.
Tips for Maintaining AC Efficiency: Clean or replace air filters regularly, keep the condenser clean, and ensure proper refrigerant levels.

More information about AC repair in the next links;

Case Study: Diagnosing and Repairing AC in Mercedes C300 Blowing Hot Air

Background

The owner of a 2018 Mercedes C300 W205 with less than 50,000 miles reports that the AC, which previously worked perfectly, suddenly started blowing warm air. After visiting two mechanics who couldn’t diagnose the problem accurately, the owner took the vehicle to a Mercedes dealership. A qualified technician conducted a comprehensive diagnostic process to identify the root cause of the AC issue.

Initial Observations and Basic Checks

Heating System: The heating works fine, and the air gets warmer when the temperature is increased, indicating that the heating system is functioning correctly.
Radiator Fan: The fan behind the radiator is engaged, suggesting that the cooling system’s fan is operational.
Compressor Functionality: The compressor starts spinning when the AC is turned on and stops when it is turned off, indicating that the compressor is mechanically functioning.
Pressure Readings:
- Low side: 105 PSI
- High side: 110 PSI (both readings remain the same with the engine off)
These pressure readings are unusually high and nearly equal, indicating a potential issue with the refrigerant flow or a blockage within the system.

Diagnostic Trouble Codes (DTCs)

The SnapOn scanner revealed several DTCs:

B107D-15: Additional Coolant Pump Malfunction (short circuit or open circuit)
B10A2-07: Actuator Motor for Left Blend Air Flap Malfunction (mechanical fault)
P0597-00: Coolant Thermostat Electrical Fault or Open Circuit (recurrent after clearing)
B113-15: Temperature Sensor ‘Right Footwell Vent’ Malfunction (short circuit or open circuit, current, stored)

**Diagnosing the Problem AC in Car Blowing Hot Air**

Key Data from Climate Control System

Causes for Shutoff of Refrigerant Compressor: No approval through C.U Combustion Engine
Power Request to AC Compressor (A9): 0.0%
Power Consumption of AC Compressor Regulation Valve (A9/7y1): 0 mA
Refrigerant Compressor Magnetic Clutch (A9/7y2): Open
Refrigerant Pressure Sensor (B12): 140 PSI
Evaporator Temperature Sensor (B10/6): 104°F
Outside Temperature Sensor (B14): 89.6°F
Coolant Temperature: 167°F
Supply Voltage of Component ‘Governor’: 12.200V

Analysis and Diagnosis

Based on the data and observations, several key issues were identified:

Equal Pressure Readings: The almost identical low and high-pressure readings indicate a possible blockage or non-functioning expansion valve, preventing proper refrigerant flow.
Compressor Regulation Valve and Clutch: The compressor regulation valve has no current draw (0 mA), and the magnetic clutch is open, suggesting that the compressor is not being activated properly by the system.
DTC P0597-00: The recurrent coolant thermostat fault could be affecting the overall engine and AC system’s performance.

Detailed Diagnostic Steps

Check Refrigerant Levels and Leaks: Verify that there are no leaks and that the refrigerant levels are correct.
Inspect Expansion Valve: Given the equal pressures, inspect the expansion valve for blockages or failure.
Compressor Functionality: Test the compressor’s electrical connections, clutch operation, and regulation valve to ensure they are functioning correctly.
Sensor Functionality: Test the temperature sensors and actuator motors, particularly the ones with stored or recurrent faults.
Thermostat and Coolant Pump: Address the thermostat fault and check the additional coolant pump for proper operation.

Repair Plan

Refrigerant System:
- Recharge and Leak Test: Recharge the system with the correct amount of refrigerant and perform a leak test.
- Expansion Valve: If a blockage is confirmed, replace the expansion valve.
- Compressor Replacement: Upon further inspection, it was determined that the compressor was faulty. Replacing the compressor resolved the issue, and the AC started working correctly.

Conclusion

The AC issue in the 2015 Mercedes C300 W205 was primarily caused by a faulty compressor. By replacing the compressor, the AC system was restored to its optimal functioning condition, ensuring the vehicle’s cabin remains cool and comfortable. Additionally, addressing minor electrical and sensor issues contributed to the overall efficiency and reliability of the AC system.

Preventive Measures

Regular Check-ups

Scheduling regular AC inspections can help catch problems early.

Scheduling Routine Inspections: Have your AC system checked by a professional at least once a year.

Proper Usage Tips

Using your AC correctly can prolong its life.

Best Practices for Using Car AC: Avoid running the AC at maximum capacity for extended periods and use the recirculation mode to reduce the load on the system.

Keeping the System Clean

Cleanliness can prevent many AC problems.

Regularly Replacing Air Filters: Change air filters every few months to ensure optimal airflow.
Cleaning the Condenser and Evaporator: Keep these components free of dirt and debris to ensure efficient operation.

Conclusion

A car AC blowing hot air is a common but fixable problem. By understanding the causes, diagnosing the issue correctly, and applying the appropriate solutions, you can restore your AC to full functionality. Regular maintenance and proper usage are key to preventing future problems. Stay cool and comfortable by keeping your car’s AC system in top condition.

AC In Car Blowing Hot Air : Case study & Solution