How To Fix Your AC Blowing Hot Air In Your Car
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Air conditioning (AC) in a car doesn’t get much attention until it stops working. When this happens, the effects of driving around in a glass-enclosed box quickly become evident. A commute or other trip turns into a miserable journey that gets worse with each mile. So, learning how to fix the AC blowing hot air in a car is essential.
Keep reading as we provide an overview of the repair process. Even if you’re not the DIY type, knowing the basics of how to fix the AC blowing hot air in a car will make you feel more comfortable at the repair shop. Importantly, never attempt a repair if you’re unfamiliar with the process or are uncomfortable with the work. Instead, seek the services of a professional mechanic.
Step 1: Check Refrigerant Levels
The most common cause of an AC blowing hot air is a low refrigerant level. Refrigerant is a special fluid that gets compressed into a cold gas and pumped through the air conditioning system. The cooling process fails if there isn’t enough refrigerant flowing.
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Open the hood and locate the AC compressor. Look for refrigerant lines going into the firewall. Feel along them, looking for any cold sections indicating refrigerant flow. If the lines feel room temperature along the entire length, that points to low levels. It’s time to have the system recharged by a technician. Be sure to have the lines inspected for any possible leaks to avoid the issue happening again.
Step 2: Examine Fuses and Relays
Before assuming the air conditioning compressor has failed, check the simple stuff first. Locate the AC fuse and relay in the fuse box, pull them, and check for any sign of burnout. Swap in a new fuse or relay as needed. Also, examine if the compressor clutch engages when you turn on the AC. If not, it could indicate an electrical issue versus a mechanical one.
Step 3: Make Sure the Condenser Isn’t Clogged
The AC condenser releases heat from the refrigerant into the outside air as it passes through, helping convert the refrigerant from a gas back into a liquid for reuse in the system. A blockage can interfere with the process. Examine the condenser; it’s usually located between the radiator and grille.
If it’s packed with debris, use a hose or compressed air to gently clean out the gunk. Also, check that the cooling fans turn on when the AC runs. If the fans aren’t working, the condenser won’t get proper airflow.
Step 4: Confirm the Evaporator isn’t Frozen
The AC evaporator is tasked with absorbing heat from inside the cabin. But if airflow gets restricted, it can actually freeze up from lack of warm air passing over it. Shut off the air conditioning and crank up the heat for 20 minutes to allow the evaporator to thaw. If you don’t want to wait, aiming a hair dryer into the vents can speed up melting. Just don’t overheat the plastic ducts!
Step 5: Change the Cabin Air Filter
Replacing the cabin air filter is an often-overlooked maintenance task. It should be swapped out every one to two years or 15,000-30,000 miles (check the owner’s manual for your car). A clogged filter can cause airflow issues through the evaporator.
Locate the filter, typically under the dash behind the glovebox. Pull out the component and inspect it for a cruddy buildup. A very dirty filter should be changed for a replacement to allow air to start flowing freely again.
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Step 6: Verify the Proper Coolant Level
Don’t overlook the simplest reason for AC problems: the lack of cold due to the air not getting cooled in the first place. In other words, the lack of engine coolant can trigger issues. Pop the hood to check the radiator coolant level and add more coolant as needed. Modern vehicles have a separate reservoir that makes the process easy. Check the owner’s manual for more details about checking and refilling the coolant. Importantly, NEVER open a hot radiator cap.
Next Level: How to Fix the AC Blowing Hot Air in a Car
If the previous measures are unsuccessful, it’s time for next-level efforts to repair the AC. This is when most car owners will turn to a trained mechanic. Here are the steps that are best left to a professional.
Step 7: Make Sure the Thermostat Works
The heart of the problem could lie with a thermostat that normally opens and closes by starting cold and warming up. The thermostat should allow coolant flow once the engine warms. If stuck shut, the AC won’t have a source to extract heat from. If the thermostat is constantly in the open position, there’s insufficient temperature build-up.
Step 8: Monitor the High-Pressure Line
The AC system is a carefully calibrated loop designed to handle specific pressures, so the condition of the high-pressure line is critical. If a leak develops, the pressure reading on the gauge will be lower than usual and affect AC cooling. Likewise, very high pressure points to a restriction. Both conditions require repair by a technician.
Step 9: Recharge the AC System
If the AC still blows hot air after checking the fuses, condenser, and evaporator, it’s probably time for a system recharge. There are DIY kits for this, but refrigerant can be tricky (including ensuring you’re using the correct version). So, handling this task through a professional is the surest way of avoiding any additional problems. Let the shop know you’ve already done preliminary troubleshooting steps. And make sure the AC system is checked for leaks you might have missed.
Step 10: Examine the Blower Motor and Ducts
To confirm ample cold air supply, the blower motor and ducts must also be in order. A mechanic will check the airflow at the vents while adjusting fan speeds. If the air volume seems low, there will be a further inspection for pinching in the ducts or debris. The next stage can involve testing the blower motor and replacing a faulty unit.
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Step 11: Consider Replacing the Compressor
When all else fails, chances are the air conditioning compressor needs replacement. This is the most expensive type of AC repair and is common with older vehicles. A mechanic will look for a seized bearing, grounded windings (the internal windings cause a short), or a burned-out clutch coil. The repair will also include recharging the system with new refrigerant.
Post-Repair Preventative Steps: How to Fix the AC Blowing Hot Air in a Car
Once you’ve solved the AC problem, take steps to keep your car’s air conditioning system in top condition:
- Annually inspect components like the condenser, evaporator, and hoses.
- Periodically run the AC to circulate lubricating oils.
- Immediately address any future AC cooling issues.
- Deal with minor issues right away to prevent bigger problems.
- Maintain proper refrigerant levels and change cabin filters as specified.
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