Why does my car stall when I turn on the air conditioner?

Turning on your car’s air conditioner should bring cool relief, not unexpected frustration. If your car stalls or struggles when the AC is activated, it’s a sign that something isn’t quite right. Your air conditioner relies on several systems working together seamlessly, and even a minor issue can disrupt this balance.

From increased engine load to potential mechanical faults, understanding why your car stalls when you switch on the air conditioner can help you identify the problem early and avoid costly repairs. Let’s explore the common causes behind this issue and how you can get your car back to running smoothly.

Troubleshooting car air conditioning problems

When your car’s AC isn’t performing as it should, pinpointing the issue can save time and money. Common problems include weak airflow, warm air, strange smells, or unusual noises when the AC is on. These could indicate anything from low refrigerant levels to a clogged evaporator or faulty compressor.

Is your car stalling when you turn on the AC?

This is the last thing you want when rushing to work in the morning, not to mention in the harsh Australian summer. So why is this happening?

Natrad is dedicated to helping you car keep cool under pressure. Get in touch with our team for more air conditioning advice.

Stalled vehicle meaning 

A stalled vehicle refers to a car that has unexpectedly stopped running, often due to the engine shutting off. This can happen for various reasons, including mechanical issues, fuel problems, or electrical failures. Common causes include a faulty air conditioning system adding too much strain on the engine, a malfunctioning idle air control valve, or insufficient fuel supply. A stalled vehicle typically needs to be restarted, but frequent stalling is a sign that a professional mechanic should address the underlying issue.

What is the air conditioning system?

The air conditioning system in your car makes the cabin air temperature and quality comfortable. It is also connected to the vehicle’s cooling system and works in tandem to ensure the air you are breathing is at the right temperature and filtered.

Widely known as the HVAC (heating, ventilation, air conditioning) system, it also handles heating. The cooling side simply removes heat and moisture from the air in the vehicle cabin and redistributes it as cool, dry air.

How does the air conditioning system work?

The air conditioning system is made up of several components that may vary depending on your vehicle, however the end result is the same.

The core function is to remove heat from the air inside the vehicle cabin using refrigerant.

• Its gaseous form transforms to liquid and back while cycling through the system, separating temperatures into cold (evaporator inside) and hot (condenser outside).
• Air passing over the cold evaporator becomes cool and is delivered inside the cabin of the vehicle.

The way this happens is through a process of compression. Beginning as a gas, the refrigerant compresses into a liquid state and becomes hot by going through the compressor.

From there, the hot liquid is cooled in the condenser and transferred to the receiver drier. This component prepares the refrigerant for entry into the evaporator by removing any excess moisture.

The liquid now enters the evaporator once complete, the air circulated through the cabin is blown past the evaporator core and the heat is released.

What you feel after that is cool, dry air.

The AC system is directly connected to the engine via the drive belt and, therefore, draws its power from there. This could be part of the reason your car is stalling.

Why is my car stalling when I turn the AC on?

Your car’s air conditioning system draws power from the engine, and this additional load needs to be carefully managed. If the system controlling engine idle speed isn’t functioning properly, the added strain from the AC can cause your car to stall. Here’s a breakdown of why this might happen:

• Engine load from the AC: The AC system increases the engine’s workload. If the engine isn’t equipped to handle the extra demand, it can lead to stalling.
• Idle Air Control (IAC) valve malfunction:
  • The IAC valve, also known as the idle air sensor control motor, regulates the air bypassing the throttle plate in fuel-injected engines.
  • This ensures the idling speed adjusts to meet the needs of various systems, including the AC.
  • A fault in the IAC valve, such as dirt or carbon buildup, can cause poor idling or stalling because the engine can’t maintain the necessary idle speed.
• Inadequate idle speed: If the IAC valve isn’t working correctly, the engine may idle too low to sustain the AC’s load, causing it to stall when the AC is switched on.

If your car stalls when the AC is turned on, it’s essential to have the issue diagnosed and repaired promptly. A professional technician can inspect the IAC valve and other related components to ensure your engine runs smoothly, even with the AC in use.

Can a bad AC compressor cause a car to stall?

Yes, a bad AC compressor can cause your car to stall, and here’s why. The compressor is a critical component of your air conditioning system, responsible for pressurizing refrigerant and circulating it through the system. However, when the compressor malfunctions, it can create issues that put undue strain on the engine. Here’s how:

• Increased Engine Load:
  • The AC compressor is powered by the engine via the drive belt.
  • When the compressor is failing, it may require more power to operate, placing excessive load on the engine.
  • If the engine can’t handle this additional demand, it may stall, especially at idle.
• Seized Compressor:
  • A seized compressor can cause the drive belt to stop moving, which may affect other engine components connected to the belt system.
  • This sudden stoppage can lead to the engine stalling as it struggles to cope with the disruption.
• Faulty Compressor Clutch:
  • The compressor clutch engages and disengages the compressor as needed.
  • A malfunctioning clutch can prevent the compressor from disengaging properly, causing continuous strain on the engine and leading to stalling.
• Electrical System Impact:
  • A failing compressor can sometimes cause electrical issues in the AC system.
  • If the electrical system is overloaded, it can interfere with engine sensors, leading to erratic idling or stalling.
• Refrigerant Blockage:
  • A failing compressor may not circulate refrigerant properly, leading to blockages in the system.
  • These blockages can create pressure imbalances, forcing the engine to work harder and potentially causing it to stall.

So, what are my next steps?

If you suspect the Idle Air Control (IAC) valve is causing the issue, cleaning it can often restore proper functionality. Built-up dirt or carbon deposits may be blocking airflow, and a thorough clean might be all that’s needed to get your engine idling smoothly again.

For more serious problems, like a seized AC compressor, it’s sometimes possible to manually release the belt. However, this requires careful handling and a solid understanding of your car’s components.

If you’re unsure or uncomfortable tackling these fixes yourself, it’s best to leave it to the professionals. At Natrad, our experienced team can accurately diagnose and resolve any air conditioning issues, from faulty IAC valves to compressor repairs. Visit your nearest Natrad store for expert service and get your car’s AC system back in top shape.