Is Your Car’s AC Blowing Hot Air? How to Diagnose & Fix Yourself

If the AC in your car is blowing hot air, there are a few different parts of your vehicle you’ll want to inspect. With this post and video, you’ll find out how to check your car, truck, or SUV’s air conditioning (AC) system for problems like the AC not blowing cold air, the AC blowing warm air, or it leaving you with a wet carpet.

Why Is My Car’s AC Blowing Hot Air?

Mechanic in front of a car reviewing how the AC can end up blowing hot air

Your car’s AC is blowing hot air because of a minor problem with the air conditioning system you can fix yourself, or because of a larger one that will need professional experience.

While the AC system is a sealed system with refrigerant that needs a special tool, like a recovery, recycle, or recharge machine, to be worked on, there are some preliminary checks you can do that mix fix any problems you run into.

You can check these parts before you decide to have a professional mechanic look at the system.

AC System Parts to Inspect If Your AC Is Blowing Hot Air or No Air

How to inspect a car with an AC blowing hot air and not cold air

  1. Check the AC Condenser and Cooling Fans

    You’ll want to start at the front of the vehicle where the AC condenser is located. The condenser looks similar to a radiator, and it’s often in front of the radiator. The AC condenser will need clean cooling fans to work so that the refrigerant flowing through the condenser can cool down.

    Inspect the Cooling Fans for Debris and Functionality
    Since you need airflow to cool down the condenser, you need the cooling fans to work. The condenser won’t cool down if they’re only partially working. The AC might not work well or at all.

    Make sure there is no debris on the cooling fans. Debris like leaves in front of the condenser or cooling fans will affect the AC system’s ability to work. If you find any leaves, dirt, mud, or other debris, clean it off. You can do this with a garden hose.

    You can even turn on the AC system and see if the cooling fans work. The fans might not work because of faulty motors, a bad relay, blown fuse, or another electrical issue.

    On most vehicles, once the AC is turned on, both fans should be on at almost full capacity.

    Inspect the AC Condenser for Leaks or Damage
    The AC condenser works by having compressed refrigerant enter one side, and as it travels through the airflow from the front of the car and cooling fans cool it off before the refrigerant exits.

    Check the condenser for stains, which is a sign of a leak. This is especially common in the lower or upper corner areas. The condenser might also have damage, which can cause a leak and symptoms in your car like the AC blowing hot air. Make sure the condenser has no punctured or broken lines.

    More on how to inspect the AC condenser

  2. Check the AC Compressor

    The AC compressor makes up most of the AC system. It pumps refrigerant throughout the system and is driven by a belt that spins a pulley. When the compressor’s clutch is engaged, it engages the compressor. This will compress refrigerant and push it throughout the AC system.

    Check the AC compressor’s belt. If it fell off, the compressor won’t work. Take a look at the belt for wear. You might just have to replace the belt. Often there’s a tensioner or idler pulley that has seized up, and that’s actually just what needs to be replaced. That can also pop the belt off.

    Turn on the AC system and watch it. If the belt that goes around the compressor pulley is working fine, listen for the compressor clutch kicking on and off rapidly. That’s an indication of low refrigerant. If refrigerant is low, it’s because there’s a leak in the system. You’ll need to bring your vehicle to a professional and have them use a special machine to fix it.

    You’ll see lines and hoses connected to the compressor. You may see stains where it looks like oil is leaking, which most likely means refrigerant is leaking. The leak will need to be repaired before adding more refrigerant to the system.

  3. Check the Evaporator Core

    The EVAP core is behind the firewall. It’s attached to lines and works similar to a radiator. Hot air goes through the EVAP core where it cools down to give you cold air from the vents. If there’s no flow, it won’t be able to cool the air down, leaving you with an AC in your car that is not blowing cold air.

    If the EVAP core is plugged with debris like pet hair, leaves, or pine needles, the air won’t flow as well. Weak airflow could be a sign that you just need to remove the cabin air filter and possibly the blower motor. Once you’ve got enough space to work with, you can get in this area and vacuum it out.

  4. Check the Cabin Air Filter

    If you find your AC has weak airflow from the vents, making it feel hotter in your car than it should, you might have a bad cabin air filter. The filter could be dirty and clogged with debris like leaves, pine needles, or acorns.

    The cabin air filter is located behind the glove box in its own compartment in most vehicles. Remove and it, and replace it if you find it’s dirty and full of debris.

    More on how to check the cabin air filter

  5. Check the Drains

    The drains let the AC system leak out water. That’s why on a hot day after driving with the AC on, you’ll notice water stains underneath your car.

    If the drains are plugged with leaves or pine needles, you may find water dripping on your feet or the carpet instead of outside your car.

  6. Check the Blower Motor

    If you turn on the AC and find no air blowing from the vents, there might be an issue with the blower motor. The blower motor resistor or the blower motor might not be working. There could be a problem with the wiring or a blown fuse.

    More on how to inspect the blower motor and blower motor resistor

  7. Check the Electrical System or Fuses and Relays

    Check the fuses and relays. Fuses don’t blow on their own, so if you find a blown fuse, that’s an indication of an electrical problem.

    More on how to diagnose fuses

    You can test the relays by swapping one relay with another known relay. Find a relay with the same number as the one you’re testing, switch them, and then see if it’s still working.

    More on how to diagnose relays

What Do I Do If the AC System Parts Are Working?

Don’t Just Add More Refrigerant

If you find there are no problems with the parts above in your car and the AC is still blowing hot air, there’s most likely a leak in the system. You don’t want to just add more refrigerant to deal with a leak. We recommend bringing your vehicle to a professional mechanic so they can inspect and repair your car with the right tools.

More on why you should not just add refrigerant

Fix an AC blowing hot air in your car yourself with quality auto parts and tips at 1aauto.com

Learn to Fix More on Your Car Than an AC Blowing Hot Air

Learn how to diagnose and fix many different kinds of parts on your car with our how-to videos. Our videos have step-by-step instructions from experienced mechanics to help with model-specific repairs and general tips.

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Car AC Blowing Hot Air? - How to Diagnose and Fix - Expert Tips - 1A Auto
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Car AC Blowing Hot Air? - How to Diagnose and Fix - Expert Tips - 1A Auto
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If the AC in your car is blowing hot air, find out how to diagnose and fix it yourself with these tips from our experienced mechanics.
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