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When you turn the knob to turn on the AC, the last thing you want is consistent hot air coming through the vents. But while a car AC blowing hot air is an inconvenience, it’s not something you have to live with.
We’ll go over some of the most common symptoms and causes of a faulty AC system, and we’ll even give you a few tips to try and figure out what’s going on for yourself before you take it to the shop. That way you can put those hot summer days behind you by turning on the AC when you get into your car.
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Before you dive in and start trying to fix things, you need to ensure that there’s actually something wrong with the AC system. There are a few different ways your AC system could be telling you there’s a problem, and we’ll highlight them for you here.
1. Blowing Hot Air
Chances are you’re here because you have a car AC blowing hot air. It’s the most common problem vehicle air conditioners go through, and it’s a big problem considering the entire job of the AC system is to blow cold air.
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Keep in mind that when the air conditioning starts to blow hot, it doesn’t have to be extremely “hot” to be a problem. Even if it’s just not blowing as cold as it used to, that’s a sign that something else is going on.
2. Low Airflow
When you turn the air conditioning on you expect to feel the air coming out of the vents. If you turn the air onto full blast and you’re not getting the same airflow that you used to, or you’re not getting any airflow at all, that’s a problem.
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3. Weird Sounds or Smells
While you might not see them, there are tons of electrical components and moving components in your vehicle’s AC system. If an electrical component is grounding out into something or if a moving component has excess resistance, it’s going to start to heat up.
This heat causes things to burn, and that burning smells. You could smell melted rubber from the electrical lines, melting plastic from moving components, or something else, but if you notice an odd smell coming from your AC system, turn it off and have someone check it out.
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- Complete Gauge Set: Orion Motor Tech's AC gauge set includes a 4-way gauge, four hoses, two quick couplers for R1234yf & two for R134a, one self-sealing can tap for R1234yf & one for R134a, plus two 1/4" male to 1/2" female adapters (LH & RH threads)
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6 Causes of a Faulty AC System
Now that you know about some signs your AC system will give you when it’s not working properly, it’s time to dive into some potential causes. There are a lot of different components in your vehicle’s AC system, so it’s not always a straightforward fix.
But understanding what different components can break is the first place to start when you’re trying to figure out how to fix it.
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One free scan finds every outdated or missing driver and matches the right update for your exact hardware.Free scan · exact hardware match1. Low Refrigerant
Low refrigerant is the number one problem when your AC system starts blowing hot. Keep in mind that if the problem is low refrigerant, it usually doesn’t go from ice cold to hot overnight.
Unless there’s a severe leak in the system, it’s usually a gradual process. The good news is that as long as there’s not a leak, it’s generally a pretty straightforward and easy fix.
2. Faulty Thermostats
While your vehicle has a thermostat in the engine bay when we’re talking about a faulty thermostat in the A/C system we’re talking about all the knobs you use to control the AC inside your car.
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Even if everything in the AC system is working, if the controls that tell it what to do aren’t working, you won’t feel the difference inside the cabin. There are a lot of electronics and motors behind those knobs, and if any of them aren’t working right neither will the AC.
3. Broken Compressor
A lot of the time people replace the refrigerant only to find that the air compressor was the real problem. It’s one of the most common components that actually fail in the AC system, but it’s also one of the most expensive.
But if you’re trying to get cold air in your vehicle, that’s not going to happen if you have a damaged or faulty air compressor.
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4. Clogged/Broken Condenser
A damaged or clogged condenser can present itself in many ways, but the most common issue is reduced airflow. The blower motor will run just fine, but you still won’t get the airflow out of the vents, and there’s a good chance the air that is coming out is warmer than you want it.
5. Electrical Problems
Your vehicle’s air conditioning system has electrical lines all over the place. They run to the compressor, to the knobs inside the cabin, to the blower motor, and more. If there’s a problem with any of these electrical lines the AC won’t work properly.
It could be as simple as a blown fuse or something more complicated like a broken or crossed line. Either way, if the electrical system is out of whack, so is the AC.
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- Complete Gauge Set: Orion Motor Tech's AC gauge set includes a 3-way gauge, three hoses, two quick couplers for R1234yf & two for R134a, one self-sealing can tap for R1234yf & one for R134a, plus two 1/4" male to 1/2" female adapters (LH & RH threads)
- Precision Gauges: This R1234yf gauge set features high and low pressure gauges with a durable oil-filled core that resists wear & shock and a dry dial for improved winter performance. Calibration screws ensure accuracy within 1.6%
- Color-Coded Hoses: The color-coded PVC hoses of this HVAC gauge kit have 4 reinforced layers to work with pressure up to 600 psi (burst pressure: 3000 psi)
- Wide Application: This air conditioning line repair tool works with R1234yf, R404a, and R134a refrigerants; ideal for HVAC maintenance, this R1234yf AC recharge kit allows you to measure pressure, evacuate and refill coolant
- Enjoy for Years: This manifold gauge set is made with a durable aluminum body and features pure copper fittings for long-lasting use and effective rust and corrosion resistance
6. Broken Blower Motor
Alright, so the main point of this article is about a car AC blowing hot air, and while that won’t happen if you have a broken blower motor, it’s a common enough problem that we felt the need to highlight it here.
The blower motor is what pushes the air throughout the system and out of the vents, so if it’s not working properly then you’re not going to have the air movement you want when you turn on the air conditioning system.
How To Fix a Faulty AC System
When you turn the knob and have a car AC blowing hot air, the first thing you want to do is fix it. If you don’t have any tools, then it’s like playing a game of whack-a-mole, hoping you find out what’s going on. Of course, the alternative is to take your vehicle to a repair shop and pay them to troubleshoot and figure out what’s going on for you.
You can start with a bottle of AC refrigerant — and it’ll give you the current charge in the system. This is generally a great place to start if your vehicle still has AC, but the car is not cold enough.
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The good news is that if you still have the bottle of AC refrigerant, you can store it and the next time your car AC is acting up you can use it!
Final Thoughts
If you’re dealing with a car AC blowing hot air then it’s time to have someone check it out. Not only is it uncomfortable for you, but if you have seized up components it could lead to further engine damage.
You could even end up with a blown serpentine belt while you’re driving down the road if the compressor seizes up! So, see if a bottle of refrigerant can’t fix your problem, but if it can’t, go ahead and take it to a professional so you don’t have to deal with a scorching hot cabin every time you get behind the wheel.
