Ever had problems with your car about air conditioner, or AC, not blowing cold air when the car is at stop? This happens in most cars when the AC system of your car does not have properly maintenance and it definitely makes you irritated to stay in the car on a hot day with no cool AC. It is necessary to check your AC systems from time to time especially when involving travels, long and short, but in order to understand why this happens, you must first know the basics of a car air-conditioning system.


Car Air-conditioning Basics

Car Air-conditioning Basics

Below are five major components of the automotive AC system:

1. Condenser

Up front, on the high- pressure side of the system you have the condenser, which is mounted in front of the radiator.

2. Compressor

Behind the condenser, you have the compressor. This moves the refrigerant throughout the system and is driven by a belt in on the front of the engine.

3. Evaporator

Behind the compressor, you have the evaporator. The evaporator is inside the passenger compartment, which is the low- pressure side of the system. It is basically where you get your cold air from.

4. Metering orifice

Attached to the evaporator is a small device called the metering orifice. What this does is it works off of the pressure-temperature relationship of the refrigerant.

5. Receiver drier

Lastly, we have the receiver drier. It functions as a way to remove moisture from the AC system. Moisture inside the AC system will compromise its efficiency.

A more detailed explanation and description of the major components of AC systems is given in this video:

Pressure-Temperature Relationship

To demonstrate the pressure-temperature relationship, let’s say for example that you have a can of compressed air. If you notice, when you spray the compressed air can for a long period of time, the can starts to get hot. Why is that? Well, the liquid inside of the compressed air can is at a high pressure.

When you let it out through the can’s nozzle, the compressed air is subjected to a lower pressure area. Then, because the material goes from a high pressure to a low pressure, it basically takes heat with it. And in understanding what air conditioning system really is, think of it as a heat exchanger where it takes the heat in your car and moves it out from your car.

If you open up the hood of your car and look at what’s mounted up front, you will see the condenser. This is where the heat inside your car passes through to be transferred outside. Behind it usually thicker than the condenser is the radiator. The condenser is actually connected by rubber and metal hoses down to the compressor.

Now, the compressor is usually driven by a certain belt in on front of your engine. Normally, the compressor can freewheel and spin, but when you press the button to activate the air conditioner inside your car, there’s an electromagnetic clutch that activates and causes the whole compression wheel to spin as a unit. The compression wheels turn the piston units inside the compressor assembly itself and refrigerant is taken in and pumped out.

We now have the evaporator. This is the one that is located inside your dashboard and is the cold-side of the system. If you examine the evaporator closely, you’ll see an expansion valve. This expansion valve is basically that small hole on the nozzle of the compressed air can that we talked about earlier.

The only difference between the expansion valve and the nozzle of the compressed air can is that the expansion valve works as a throttle it opens and closes the hole depending upon the refrigerant demand. This expansion valve is the one that prevents the evaporator from turning into one giant block of ice.

Causes of No Cooling During Idle and How to Solve Them

1. Lack of condenser air flow

The first culprit of your car air-conditioning not giving off cold air when the car idling is the lack of air flow in the condenser. What you can do is check whether the electric cooling fan that sits beside the condenser is running. Check whether the electrical connections for the condenser fan is connected and seated firmly.

2. Low levels of Freon

Make sure that the Freon level on the compressor is within acceptable levels. If you know how to gauge and refill Freon, do it. If your air conditioning mechanics is not up to par, then have a certified car air-conditioning system mechanic check it for you.

3. Overheating

Lastly, the reason why your car air-conditioning isn’t blowing cold air is because your engine is overheating. Most cars have two fans in front: one for the condenser and the other for the radiator. Always make sure that both fans are running at designated speeds. Both fans should be running even if the car air-conditioning is turned on during a hot summer day.

Just a small note to remember, whenever the car is moving at freeway speeds, Freon is pumped throughout the air conditioning system more easily by the compressor compared to when the car is sitting idle. There is a noticeable air flow increase in the condenser whenever the car is running at speeds in excess of 55 mph.

There are times when your refrigerant is outdated and you cannot find an AC gauge set that fits your refrigerant, which is needed for checking levels of Freon, purchasing an AC conversion kit helps to make it easier for you gauge and refill Freon. The most recommended kit is the Mountain 8201 R-12 to R-134a Conversion Quick Connect Coupler Set, which can be bought at



So, there you have it. You have basically learned the basics of an automobile air conditioning system, which helped in understanding how and why most car air-conditioning units fail to blow cold air when idle. If you’re having this exact problem, don’t hesitate to try out our recommendations and comment any clarifications you have. You might also find the given link helpful in solving your problem.

Just remember these three main culprits when such problems occur:

  • Check for lack of condenser air flow
  • Check for low level of Freon
  • Check for engine overheating

If you have tried all of these and none works, have a reliable mechanic check it for you.

If you have some questions about or suggestions for this article, kindly leave them in the comments section. You can also share this article with your friends and family if you liked it!

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Chief editor at Paul's Gigantic Garage. I came up with this blog to help you to sort out some basic problems your car may be facing and in turn, save lots of cash by some of my DIY tips that I hope will get your car out of its current situation. I also had in mind motor enthusiasts who for the love of cars who are constantly looking for information about cars on the latest trends, questions, fixes, driving, tricks, and accessories.


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