Why car ac works only when driving

Why Does Your Car AC Only Work When You’re Driving?

As a car owner, you must have experienced having your car’s air conditioner work well when you are driving but not when you have parked your car or when ideal. Sitting in the heat while your car is parked is inconvenient and frustrating. You need to consider what is wrong with your car’s air conditioning system and whether it is a serious problem.

In this post, we’ll go through some reasons why your car’s air conditioner isn’t working properly and offer you the best repairs.

Why car ac works only when driving [5 Reasons]

Why car ac works only when driving 5 Causes

If your car only starts when you are driving, it could be a sign of a problem. The problem may not be very serious, but it is important to identify and locate it to prevent further damage to your vehicle.

Here are some of the many explanations that make your car air conditioner work only when you are driving.

Low refrigeration

Low refrigerant prevents the system from producing enough pressure, ultimately reducing the cooling capacity. Several factors can cause a refrigerator to be downgraded. Some may be due to leaks, broken valves, or improper charging.

Low refrigerant can damage the compressor and other parts. Therefore, it is important to check and monitor your refrigerant levels on a regular basis to ensure efficient cooling.

Faulty condenser fan

The condenser fan is the part that cools down the refrigerant after it passes through the compressor. It is located close to the radiator and normally comes on when the air conditioner is turned on.

The refrigerant won’t be able to condense and cool down if the fan is malfunctioning, especially while the car is ideal or parked. A defective motor, a blown fuse, a faulty wire, or an obstruction are possible causes of this.

Damaged compressor

A damaged compressor will obstruct the successful pumping of the refrigerant and sustain the cooling cycle. Wear and strain, a lack of lubrication, excessive heat, or electrical problems can all contribute to this.

Faulty expansion valve

The component that controls the flow of refrigerant into the evaporator, where it cools and transforms from a liquid to a gas, is the expansion valve. The valve won’t be able to change the refrigerant flow in response to changes in temperature and pressure if it is blocked or jammed. When the car is idle or parked, the ac may not work ineffectively or at all.

Electrical problem

The ac system depends on several electrical parts, including cables, relays, sensors, switches, and fuses. The operation of the ac system may be hampered or rendered inoperable if any of these parts are flawed or damaged. For instance, if the compressor clutch switch is damaged, the compressor cannot be engaged or disengaged when it is required.

How to Fix a Car ac that works only while driving?

car mechanic inspecting Air conditioning

Fixing the car air conditioner is necessary if it works only while driving. Here is a guide and some measures you may take to fix this issue: 

1. Checking refrigerant levels

Low refrigerant levels are one of the most frequent causes of a car’s air conditioner operating only while you are driving your car. When the car is ideal or not moving, the AC won’t be able to create enough cold air if the refrigerant level is too low. You will need a refrigerant gauge and a refrigerant kit to check and replenish the refrigerant level. These kits are available online or at any auto parts store. 

Here is the step-by-step guide you may follow to check the refrigerant level:

  • Find the AC system’s low-pressure port. Typically, it is close to the firewall on the passenger side of the engine compartment. It features a hat with an L on it in either black or blue.
  • Connect the low-pressure port of the refrigerant gauge. Make sure the connection is tight and that it doesn’t leak.
  • Start the engine of your car and crank up the air conditioning. The compressor should turn on, and the gauge should read something.
  • Compare the gauge reading to the pressure range advised for your automobile. This information can be found in your owner’s handbook or on a sticker beneath the hood.
  • If the reading falls outside the suggested range, more refrigerant must be added. Follow the instructions on the package and fasten the refrigerant kit to the gauge to do this. Avoid overfilling the system since doing so might harm or start a fire.
  • You do not need to add more refrigerant if the reading falls within or exceeds the advised range. Your AC system could be experiencing yet another problem.

2. Inspecting and repairing the condenser fan

A malfunctioning condenser fan is another reason why a car’s air conditioner may only operate while the vehicle is moving. After the refrigerant has passed through the condenser, it is cooled down by the condenser fan, which is a sizable fan. In front of your car’s radiator lies a radiator-like component called the condenser. If the condenser fan malfunctions, the refrigerant will not cool down sufficiently, causing the air conditioner to blow warm air. A multimeter and other simple equipment are required to examine and fix your condenser fan.

Here is the step-by-step guide you can follow:

  • Find the condenser fan in the engine compartment. The condenser, located in front of your radiator, is often behind or below it.
  • Check to see if the fan blades are corroded or filthy. If they are, scrub them with a soft brush or, if required, replace them.
  • Verify the fan motor’s functionality. To accomplish this, start your car and crank the air conditioning all the way up. It should take a few seconds for the fan to begin spinning. Alternatively, switch off your vehicle and unplug the fan connector from the electrical harness.
  • To check whether the fan motor is receiving electricity, use a multimeter. One probe should be placed on each terminal of the fan connection after setting your multimeter to DC volts. Get a reading of 12 volts or higher, at the very least. If you don’t, there could be an issue with the fuse or the wiring.
  • The fan motor has to be replaced if it receives electricity but does not spin. A replacement fan motor is available in any car parts store or online. You will have to take the old fan motor out of its mounting bracket and put the new one in its place to replace it. Make that the wire harness is appropriately reconnected.

3. Addressing compressor issues

A compressor issue is another reason a car’s air conditioning can only operate when the driver is in motion. Your air conditioning system’s compressor compresses and circulates refrigerant. It is powered by a belt attached to your engine’s crankshaft pulley. Your air conditioner will spew warm air if the compressor is seized, broken, or worn out and unable to compress enough refrigerant. You’ll require the assistance of a qualified mechanic to solve compressor problems.

Here are some indicators that you may have a compressor issue:

  • When you turn your AC on or off, it generates a lot of noise.
  • Even if you have adequate refrigerant and a functional condenser fan, your air conditioner still blows warm air.
  • Your air conditioner regularly turns on and off or doesn’t turn on at all.
  • If you turn your air conditioner on, your engine may overheat or lose power.

The following measures must be taken to replace or repair the compressor.

  • Disconnect the compressor belt. Locate and remove the compressor belt from the front of the compressor.
  • The power connection may be disconnected. Check the electrical connections on the compressor; Maybe the wire came from him.
  • Disconnect the refrigerant connector.
  • Remove the compressor.
  • Install the new compressor.

D. Other troubleshooting tips

If none of them fix your problems, you may have more problems with your car’s AC system that requires thorough diagnosis and maintenance.

A few other problems can occur as follows.

  • There is a drain in the AC system that allows water or refrigerant to flow.
  • A refrigerator cannot run smoothly due to obstructions or obstructions in the air conditioning system.
  • Faulty sensors, switches, or relays control the operation of the AC system.
  • Worn or corroded wires or connections affect the electrical supply of the AC system.

Frequently Asked Questions

Why does my car AC work when driving but not when idling?

One of the main causes of air conditioning that only operates when moving might be infected condenser fans. Condenser fans aid in lowering the temperature of the refrigerant so that it condenses. This may be avoided by fixing condenser fan issues.


In conclusion, it might be annoying to be in a position where your car’s air conditioning system isn’t functioning when you not driving. A few possible causes of this problem are low coolant levels, a damaged condenser, a broken compressor, a broken expansion valve, or an electrical problem. 

It’s crucial that you locate the problem and address it right away in order to ensure vehicle safety and to benefit from effective cooling while comfortably seated in your automobile. Some quick fixes for this problem include checking the condenser line, the coolant level, and the compressor. You can follow the DIY instructions, but having a certified professional properly inspect your car is the best course of action.

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