My 2003 Hyundai air conditioning works fine but often starts blowing hot air, especially when idling.

Air conditioning has started to work sometimes and sometimes blows hot air. If the air conditioning is working fine and I have to idle at a stop light, it will almost always start blowing hot air and, usually, won't go back to blowing cold air for the rest of the trip.

My car has 115000 miles.
My car has an automatic transmission.

Experienced mechanics share their insights in answering this question :
Hi There,
It sounds like you may have a condenser fan that may not be cooling the AC condenser properly. As you may know, the job of the AC condenser fan is to cool down the AC condenser as it generates a lot of heat during the course of its primary function, which is to convert the AC gas refrigerant into a liquid form, a process that generates a significant amount of heat. As the AC condenser fan blows cool air across the condenser, this allows the condenser to remain cool, keeping the pressure down in the AC system which helps to generate cooler air. I would suggest having a professional from YourMechanic come to your location to take a look at your vehicle.

How to Identify and Fix Common car Problems ?

Our sources include academic articles, blog posts, and personal essays from experienced mechanics :

Refrigerant leaks are the most common cause for car AC blowing hot air. Low pressure in the system can occur when there is not enough refrigerant in the lines. This results in an inefficient cooling process, which can cause warm air to blow instead of cold.
The most common fault on the Hyundai Elantra air conditioning system is the discharge aircon hose leaking at the ferrule crimp. This hose is repairable by cutting off old ferrules and welding new ones on and replacing the rubber hose section. One other issue they have can be the AC compressor clutch coil shorting out.
A car A/C blowing hot air is often the result of a refrigerant leak. Refrigerant is a liquid that circulates through your car`s A/C system, expanding and contracting as it removes heat and humidity from the cabin. None of the other A/C components will function correctly without proper refrigerant levels.
The most common cause of a vehicle`s air conditioner not getting cold enough is that it needs to be recharged. You can recharge your refrigerant by yourself, but to save time and make sure the job is done correctly you should make an appointment with your local professional auto shop.
Change The Cabin Air Filter

Cabin air filters can capture dust, bugs, leaves, and other various types of debris. A dirty air filter can certainly impede your air conditioner`s ability to cool and after time could cause unnecessary strain on the entire system.

If your A/C flip-flops from hot to cold and back again, your expansion valve could be failing. The expansion valve removes pressure from liquid refrigerant to allow expansion from a liquid to a vapor state in the evaporator. If the valve is blocked, the refrigerant flow could be restricted or could be too unrestricted.
AC Works Intermittently: When the air goes from cool to warm to cool again, you`re experiencing intermittent problems. This is often due to a clog in the system, a failed compressor or compressor clutch, a faulty condenser fan, a clog in the system, or the actuator directing airflow has failed.
A common question we get is, “Why is my central air not working?” Some of the most common reasons a central air system stops working include: coolant has run too low, the air filters are blocked or dirty, the coils are frozen over, or there is an electrical issue.
Many people wonder, “Can a dirty air filter cause my AC not to cool?” The simple answer is yes – a dirty filter can create several problems that can hinder your unit`s effectiveness. Not to mention, a dirty filter can also lead to premature failure of your system.
Loud clanking or banging can also indicate that your compressor needs replacement. Rattling, ticking, rumbling: these kinds of sounds often point to a loosening piece of hardware or leaves clogged in your outdoor unit. Check for any debris, loose screws or bolts in the casing.
Compressors generally last the lifetime of a car, or approximately 12 to 15+ years depending on how well the car is looked after. In saying that, it`s important that you regularly check up on and service your car to prevent premature failure. Some ways you can tell if something is failing can include: Leaks.
The most common reasons a Hyundai Elantra ac isn`t working are a refrigerant leak, an electrical climate control issue, or a problem with the air conditioning compressor. You may not realize there`s a refrigerant leak until the air conditioner stops blowing cold.
If your car`s air conditioning isn`t blowing cold air at all (or it tries, then turns warm), you could have a clogged expansion valve, a faulty compressor clutch, a leak, or a malfunctioning fuse in the system.
If your car`s air conditioning isn`t blowing cold air at all (or it tries, then turns warm), you could have a clogged expansion valve, a faulty compressor clutch, a leak, or a malfunctioning fuse in the system.
One of the most common reasons why your engine overheats when your AC is on is a faulty engine cooling fan, fan switch, or fan motor. A bad engine coolant sensor, an overloaded AC compressor, a broken water pump, and blocked AC condenser fins can also create overheating issues.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

My 2003 Hyundai air conditioning works fine but often starts blowing hot air, especially when idling.
ANSWER : Hi There,
It sounds like you may have a condenser fan that may not be cooling the AC condenser properly. As you may know, the job of the AC condenser fan is to cool down the AC condenser as it generates a lot of heat during the course of its primary function, which is to convert the AC gas refrigerant into a liquid form, a process that generates a significant amount of heat. As the AC condenser fan blows cool air across the condenser, this allows the condenser to remain cool, keeping the pressure down in the AC system which helps to generate cooler air. I would suggest having a professional from YourMechanic come to your location to take a look at your vehicle.

While driving defroster set to hot blows hot air as it should, while idling it is blowing cold air.
ANSWER : First, the coolant level should be checked to make sure the radiator is full. While the overflow tank may be full, the radiator cap must be taken off to check the level inside the radiator. If you find the level is very low, you have a coolant leak that must be fixed. If coolant levels are normal, an engine thermostat or heater control problem may be what you’re experiencing. Consider hiring an experienced technician like one from YourMechanic who can come out and take a closer look at your lack of heat concern to offer a more personal diagnosis.

air conditioner started making loud screeching noise and started only blowing hot air, then the noise stopped but still only blows
ANSWER : The noise is possibly from a failed compressor clutch or the compressor itself is faulty. Another possibility is the pulley bearing on the front of the compressor has failed. The issue should be fairly evident to the inspecting mechanic after some simple tests. To resolve this, the recommended diagnostic is an a/c system inspection. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

When idling, car overheats and A/C blows hot air – 2001 Saturn L100
ANSWER : Hello. The most likely cause of the issue that your are having would be a faulty cooling fan. The cooling fans purpose is to keep the radiator and condenser for the air conditioning cool during the idling function of the vehicle.

If the cooling fan is not working, this will cause the radiator and condenser to get very hot. When the radiator and condenser get hot, this can cause the vehicle to overheat and the air conditioning not to work. When the vehicle is driving at higher speeds, the force of air that is created towards the vehicle will flow through the radiator and condenser and therefore keep them cool. I would recommend having the cooling fan checked to make sure that it is working properly. If not, I would recommend having the cooling fan replaced.

Hot air mixed with cold blows from air conditioning
ANSWER : Hey there. You will most likely have to have a mechanic bypass the heater coolant lines to have this resolved. Your A/C may not be controlling the air flow inside the evaporator correctly out of the vents and may be the blend door actuator stuck in the heat position. Have the AC system diagnosed first before bypassing the heater.

Air conditioning is blowing hot air – car stalls when A/C is on
ANSWER : In order to diagnose all the different problems you have, I having the A/C pressures checked to see if the system is low on refrigerant from a leaking compressor or another component. The rough idle may be due to a dirty throttle body and idle control system. If you would like to have this checked for you, a certified professional from YourMechanic can come to your car’s location to inspect the A/C and rough idle in order to proceed with the proper repairs.

In a 2003 Cadillac CTS at idle position, it does blow hot air but once driving, I only feel cold air coming through the vents.
ANSWER : Hi there. It is possible that you have an obstruction of engine sludge or debris inside the heater core. This typically will cause elevated engine temperature and heaters to not work as well during operation; or specifically – when the heater control valve is opened during operation. It’s also possible that the heater control valve is not working as intended; which might explain the cooler air during engine operation. I would first suggest reading this article which explains some of the common symptoms of a failing heater control valve. If these are common with your issue, it’s probably best to have a professional mobile mechanic come to your location and complete a heater is not working inspection to determine the source of this issue.

My air conditioner blows warm when idle, looses coolant and starts to overheat.
ANSWER : Hi! I have a couple of thoughts that may help you sort out the issues with your Explorer. There may be separate root causes of the issues with the air conditioning system and the cooling system.

The first thing I would do is a pressure test on the cooling system. This will help to identify whether there are any leaks in the cooling system.

Something as simple as a faulty radiator cap can allow coolant to bubble over out of the radiator. I would just put a new radiator cap on it.

Your engine may actually have a blown head gasket. One of the symptoms can be engine compression leaking into the cooling system and over-pressurizing it to the point of pushing coolant past the radiator cap and out of the overflow. There is a testing tool that can can be helpful called a block tester. It is used to identify the presence of combustion gasses in the cooling system.

A qualified technician from YourMechanic can come to your home or office to inspect your AC system and recommend the best path to repair.