Eddie spent 35 years in the automotive business with Honda. He is an ASE Certified Master Technician and has bruised knuckles to prove it.
Why Is Warm Air Coming Out of the Car's AC?
As the warm days approach us, we reach for the AC button on the dash. But we may be disappointed to find warm air, not cold, coming from the car's AC system.
When this happens, a customer's first thought is that the AC system needs to be charged. And a lot of mechanics will do just that, if you come in with this complaint. But is it the right solution, or are you throwing money out the window on a temporary repair? If a leaky AC system is low on refrigerant, charging it will cause the AC to start working again, but it's only a matter of time before the freon leaks out and stops working again. Just putting more refrigerant in a leaky system is the wrong solution. You need to fix the root problem first, then charge the AC system as needed.
I'm going to cover some common problems that both consumers and mechanics overlook when the car's AC isn't working or isn't cold enough. Recharging the AC system with refrigerant is not always the answer. There are several reasons a car's AC will stop working, and a low refrigerant charge is only one possibility and often not the most important one.
Video: Checking the AC System on a Lexus and on a Ford
The Most Common Reason Your Car's AC Isn't Cold
The most common reason for your car's AC not blowing out cold air is that it is low on freon. And the most common reason for it to be low on freon is that there is a leak in the AC system somewhere.
Leaks can be found in any part of the AC system's lines and components. Here are three common places you can check for leaks yourself.
1. Most Common Location for Leaks: The Condenser
The most common type of AC system leak is at the condenser. Because of its location, right in front of your car's radiator, the condenser takes a lot of hits from debris that bounces up from the road and the tires of the cars in front of you. We have all experienced a rock hitting the windshield and causing a chip or crack. Now imagine that same rock hitting a soft aluminum condenser; it sometimes slices the small tubes wide open, causing the freon to escape instantly, and leaving us a little hot under the collar.
If your AC system immediately stops blowing cold air, you can do a quick inspection of your car's AC condenser by looking through the front grill of the vehicle with a flashlight. Look for any dark oily wet spots. You may even notice a few dents where rocks and debris have already hit but didn't penetrate the condenser.
The best time to do this type of inspection is on a dry day. If you try to inspect the condenser on a rainy day after a drive, the rain will make it difficult to see any wet or oily spots.
If you do notice any abnormalities it may be time to have an AC expert diagnose the issue and verify the condenser is the problem.
I have a few pictures below showing what these dents and leaks look like and what to expect when looking for this type of failure.
What AC Condenser Damage Looks Like
Oily Spots: Telltale Signs of a Leaking AC Condenser
The photos below show oil spots on the cooling fins, made by AC condenser oil. Look for spots like these when inspecting the condenser for leaks.
2. Other AC Components May Leak, Often at O-Ring Connections
As the AC system ages, leaks will start to develop at weak points in the system, usually at connection points that use rubber o-rings to seal the system. Vibration, heat, and age can cause these o-rings to fail, resulting in small leaks and poor AC performance. Over time these small leaks can cause the system to stop working because of low freon.
The good news is we can locate these types of leaks with a fluorescent dye and an ultraviolet flashlight. The dye is bright yellow and can be easily detected using the ultraviolet light, because it glows in UV light just like those "black light" posters would glow when we were teenagers. If the mechanic suspects a small leak in the AC system, they can evacuate and charge the AC system and inject a dye during the process which will leak out over time, causing a trail of fluorescent dye that can be detected using an ultraviolet light. This method, in my opinion, is much more reliable than "freon sniffer" leak detectors which often give false readings.
Below I have some photos showing fluorescent dye leaking out around an AC compressor line o-ring.
AC Compressor Leak Detected With Fluorescent Dye
The photos show an AC compressor leaking freon that has been tagged with a fluorescent dye tracer. The leak is most likely caused by a damaged o-ring between the AC compressor and AC line. This leak could be found very easily with an ultraviolet light.
3. Leaks at AC Charging Ports
The AC charging ports can also leak from time to time. These ports are usually at the top of the engine compartment. You can do a quick visual inspection of the lines and charging ports for any oily residue or fluorescent dye.
Another quick check anyone can do is to remove the charging port caps and inspect the Schrader valves beneath for any bubbles of freon or excessive dye or oil. These Schrader valves are identical to the Schrader valves on tires. Taking the cap off the valve doesn't let the freon out, just like taking the cap off a tire's valve stem doesn't let the air out. A tiny piece of debris or deterioration of the rubber gasket can cause a leak. If you identify a leak it can save you time and money, though you may need your mechanic to repair the leak and charge the system.
It is unlawful to open an air conditioning system and release the freon into the atmosphere. Your mechanic has the tools to recycle any remaining freon and charge the system properly.
Below you can see some examples of what the charging ports and Schrader valves look like.
Visually Checking an AC Charging Port for Leaks
Quick Checks May Not Solve Your AC Problem, but the Problem Needs to Be Found
I only covered a few possible problems with the car's air conditioning system here; there are a lot more things that can fail. But I wanted to give you some quick, simple checks without going in too deep. A lot of the car's air conditioning system is buried behind the dash, body panels, and engine compartment. If these quick checks don't locate your problem, you'll want to make an appointment with an air conditioning expert. But if they tell you "the AC just needs a charge," be sure to ask them if they will fix the system for free when it comes back empty.
I can't stress enough how important it is to understand that if the system is low on freon, the system has a leak somewhere that needs to be fixed. If the system is empty or low, the mechanic will have to evacuate and charge the system, add dye, and check for leaks. If they can't find the leak right away they may have you drive the car for a few days and come back for another leak inspection. Once the leak is found, the mechanic can recover the remaining freon, recycle it, fix the leak, then evacuate and charge the repaired system, now hopefully leak-free. This process can be lengthy sometimes if the leak is not visible, but if your mechanic repairs it right the first time, your AC will work problem-free for years into the future.
FAQs About Your Car's AC
1. How Do I Make My Car Cooler?
Follow these tips.
- Park your vehicle in the shade. When your car sits in the sun the dash pad heats to about 160ºF and you can almost cook an egg on it. The air coming through the dash vents has to travel through the dash tube—that is, through something heated to 160º—before it reaches you, so I recommend you park in the shade to keep the interior of the vehicle and the dash pad as cool as possible.
- Keep your recirculation button on recirculate. The AC evaporator removes moisture from the air, and dry air not only feels cooler but is much easier to cool down. When the recirculation button is on, the cabin air is recirculated through the evaporator and most of the moisture is removed. This is the water you see dripping from under your vehicle when the AC is in operation. this is the water dripping under your vehicle when your AC is in operation) making the air feel cooler.
- Open the windows before you get in to remove extremely hot air. Some vehicles have a button on the key remote that you can hold down or click twice to make all the windows and sunroof open at once to let the hot air out. Or you just use the window switches to let out some some hot air that would otherwise have to run through the evaporator to be cooled.
- Use a windshield sunshade. Windshield sunshades do help cool the vehicle because they keep the sun from beating down on the dash pad and heating it up. Under a sunshade, the dash pad will be the same temperature as the cabin temperature, much cooler than a sunbaked dashpad.
- Tint your windows, if you can afford it and the state inspection laws in your area allow it. The difference in temperature is amazing when you compare a car with no window tint to a car with tinted windows.
2. What Are the Symptoms of a Bad AC Compressor?
- If the AC compressor clutch is worn, generally it will make a rattling noise when in operation but the AC system can still cool the vehicle.
- Internal damage to the compressor can result in a loud clunk or crunch and cause the AC system to completely stop working.
- A leaking AC compressor can result in the loss of freon over time and poor AC performance. An AC compressor will usually leak at the shaft seal located under the AC clutch.
3. How Much Does It Cost to Fix the AC in a Car?
- It all depends on what the problem is and where you live. Repair costs around the country and the world differ a lot. And it depends on what's wrong with the system. If the vehicle needs to have the AC compressor replaced the cost will range between $500 and $2500 after it’s installed, evacuated and recharged, but a leaking o-ring would be a lot less to fix
- Another factor is the type of freon that your car uses. R12 isn’t used much any more; R134A is the most common at the time of this writing; and 1234YF is the new freon that was introduced around 2018. The 1234YF freon is extremely expensive at this time and the average cost of the 1234YF freon alone to charge an AC system is about $150 - $250. This doesn't include labor or parts.
4. How Long Does It Take to Fix the AC in a car?
- Again, this all depends on the repair. A leaking o-ring could take a couple of hours including the evacuate and recharge but replacing an AC condenser sometimes involves removing the car's front bumper and grille which would add substantial time to the repair.
5. How Much Does it Cost to Recharge an AC?
- This will depend on the type of freon used (R12, R134A, or 1234YF) in your AC system and the capacity of your system (how much freon is needed for a full charge).
- Keep in mind that it's not normal for an AC system to be low on freon. If the vehicle is low on freon, that means the system leaks and should be fixed before recharging. Otherwise, you're just throwing money out the window.
How Hot Does it Get in a Car Sitting in the Sun?
This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.
Leave a Comment if You Have Questions About Your Car's AC
Tammy Winters from Oregon on August 31, 2020:
Thanks Eddie :)
Eddie Carrara (author) from New Hampshire on August 31, 2020:
Great name :) Let me know if I can answer any questions for you.
Tammy Winters from Oregon on August 30, 2020:
I need to check my Freon for my ac.... Thanks for the hub
Eddie Carrara (author) from New Hampshire on January 17, 2020:
This is not a simple fix. This problem could be caused by a few different things. The heater core could have a blockage, the dual climate control hot air door motor on the passenger's side isn't working, or the climate control panel or another computer-related part may not be working properly. I recommend you take a look under the dash on the driver's side and see if you can locate the driver's side hot air door motor by switching the temperature on the dash from hot to cold while trying to locate the motor. If you locate the driver's side hot air door motor you'll know what to look for on the passenger's side. If you do find it you could disconnect the linkage and move the door manually. I'm not sure if this is possible, but if's worth trying. Let me know what you find and how you make out, thanks.
Josh-Mason on January 16, 2020:
my 2011 avalanche heater blows hot air on the drivers side and cold air on the pass. The heat controls are both set for 25 d celsius
the outside temp today is -27 Celsius, plus wind chill. Help, Thanks Josh
Eddie Carrara (author) from New Hampshire on January 16, 2020:
Hi Liz :)
Yes, the AC always seems to let go right before a heatwave or smack dab in the middle of it lol. Thanks for taking the time to comment, it's always nice to hear from you :)
Eddie Carrara (author) from New Hampshire on January 16, 2020:
Yes, overcharging the AC system is not good either, it can cause all kinds of problems from poor performance to blowing out weak o-rings/ components. It's best to have the professionals do the evacuate and recharge because they have the right equipment to do it. Thanks for stopping by and leaving feedback
Oscar Jones from Monroeville, Alabama on January 15, 2020:
Also , i found out you dont want to just add freon recklessly. Use the gauges. Overcharged ac is as bad as an undercharged one. I sure got that explained to me why you dont. In case anyones listening.
Liz Westwood from UK on January 15, 2020:
I have read your article with great interest, as always. I once knew a fellow Toyota Previa owner who had a leak from a pipe running along the long wheelbase of her MPV. Our aircon outlets were only towards the front of the car, but her system was higher up the range. From experience, eventually after a few years, something tends to go wrong with AC, usually when you need it the most.