Why Does Car AC Only Work When Driving? Comprehensive Causes and Fixes

If your car AC only works when driving, there could be several underlying reasons. This article will take you through the technical causes and practical fixes for why a car’s air conditioner only functions while driving.

For car owners in the UAE and other areas experiencing extreme hot temperatures, an air conditioner is indispensable due to the consistently warm weather throughout the year. Not only does an air conditioner enhance driving comfort, but it also provides a cool environment when the car is parked. However, like many car components, the AC system is prone to issues such as malfunctioning, inadequate cooling, or only working when the vehicle is in motion.

A non-functional or faulty car AC can be particularly frustrating, especially in humid regions where common AC issues can significantly impact your driving experience. During pit stops or while parked at malls and other places, a non-functional AC can make the heat unbearable. Additionally, car colors and upholstery materials can exacerbate the heat effect, making it crucial to address AC issues promptly.

Car AC Only Works When Driving – Causes and Fixes

Maintaining your car AC is essential to keep it in good working condition. Here are some detailed causes and solutions for why a car AC might only work when driving.

Faulty Condenser Fans

Defective condenser fans are a major cause of air conditioning issues when the car is stationary. Condenser fans help reduce the refrigerant’s temperature, ensuring it condenses properly. Malfunctions in these fans can prevent this process, leading to AC problems.

Causes of Condenser Fan Malfunction:

• Faulty temperature switch
• Defective coolant sensor
• Stuck open car engine thermostat
• Faulty fan control module
• Dysfunctional fan motor

How to Fix

Start by cranking the car’s engine and setting the AC to maximum temperature. If the fan rotates, the fuses and relays are likely functional. However, this method does not provide conclusive information about the PCM and temperature sensors. Use a multimeter to check the temperature sensor, relays, fuses, and continuity in the fan’s wiring. Another option is to use jumper cables to power the fan motor directly from the battery. If the fan runs smoothly, it is functional. A slow-spinning fan indicates a fault, requiring replacement of parts such as relays, fuses, thermostats, and sensors.

A faulty motor can be replaced or repaired by a professional. Additionally, check for loose bolts or wire connections and use a mixture of water and baking soda to remove corrosion from wires.

Blocked AC Condenser

If the condenser fan is not the issue, a clogged condenser might be the culprit. A damaged or clogged condenser can significantly affect the air conditioner’s performance.

How to Fix

Cleaning a clogged AC condenser is relatively straightforward. Use a clean cloth or professional cleaning tool to remove the clogging source without causing damage to the condenser.

Leakage in AC

Leakages can also impact AC performance, causing it to malfunction when the car is not in motion. Addressing AC leakages promptly is crucial.

How to Fix

Diagnose the car AC for leakage problems by following these steps:

• Check coolant levels and add fluids if low.
• Examine the compressor belt for damage or looseness.
• Check air filters and replace if necessary.

These steps can help identify and fix car AC leaks effectively.

Damaged/Clogged Compressor Clutch

A damaged or clogged compressor clutch can cause the car AC to only work when driving. Symptoms include loss of power, whining and grinding noises, weak airflow, or no cold air.

How to Fix:

• Check the compressor’s wiring for intact connections. Clean and reconnect if necessary.
• Examine the clutch compressor for wear and replace if excessive.
• Inspect the clutch plate for damage and replace if severe.
• Clean the compressor clutch with a clean cloth or brush to remove debris.

Faulty Expansion Valve

A faulty expansion valve can also cause the car AC to only work when driving. Symptoms include ineffective cooling or irregular noises from the AC system.

How to Fix

• Check the unit’s power supply and switch it on if off.
• If the expansion valve doesn’t start, replace it by turning off the power, removing the old valve, and connecting a new one.

These are the major causes of why a car AC only works when driving. An air conditioner is essential in humid climates, adding comfort to your ride. While some common problems like AC blowing warm air or ineffective cooling can be fixed at home, it is advisable to seek professional help if you are unfamiliar with these processes.

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