Car AC Stops Working When Hot Outside: Causes and Solutions!


An absolute horror if you have to drive your car on a hot day and the air conditioning stops working or doesn’t cool the car off enough. We are confident that you won’t want to drive while the engine is heating up and continuously pushing hot air into your car while the temperature outside approaches 100 degrees.

These are the reasons why you need to track down those responsible for any AC-related issues. What are the reasons why your car’s air conditioning stops functioning when it’s hot outside, and how can you fix it? Let’s read the article together and discover the truth!

Why Car AC Fails When It’s Hot Outside

A car’s air conditioner is either not cool or only sometimes cool.

One of the most typical issues is when it is hot outside. This indicates that there are issues with the car’s air conditioning system. To prevent the problem from getting worse, shortening the lifespan of numerous crucial components, increasing fuel consumption, and degrading your driving experience, the reason must be identified and handled quickly.

When traveling in hot weather, your air conditioner may encounter any of the following issues:

  • Poorly functioning air conditioning system: This is when the air conditioner is on full blast, but you still don’t feel cool while driving, and there may also be times when the air leaving the cabin smells unpleasant.
  • Even if the cooling system has been turned on, the air conditioner loses its ability to cool entirely in this situation.

7 Reasons Why Your Car’s AC Is Not Working Well in Hot Weather

When it’s hot outside, your car’s air conditioning may cease working for a variety of reasons, including the following:

Clogged filter

A blocked air conditioner filter is frequently one of the reasons why the air conditioner stops operating or keeps running but does not provide adequate cooling.

A Dirty Outdoor Unit

The outside unit is often mounted in front of the engine fan and radiator. This component serves as a heat exchanger, dissipator, and heat discharger. Too much dirt buildup on the component may result in poor heat dissipation, which can significantly reduce cooling effectiveness and render your AC inoperable.

Blocked Condenser

The condenser’s job is to transform Freon gas into liquid form. It takes place during a heat exchange procedure in which the refrigerant’s heat is forced out and exchanged with ambient air. The refrigerant will cease flowing if the condenser is broken, which will stop the flow of cool air.

Refrigerant Problem

Your AC system has a gas shortage since it hasn’t had a gas refill in a while. The air conditioner will work inefficiently as a result of this circumstance and won’t pump cool air into your car.

A refrigerant gas leak is also a scenario that might cause your air conditioner to stop working. The AC system will stop functioning when the pressure falls below the normal range.

AC Lines Freezing Up

The inside unit is in charge of absorbing and lowering the air’s temperature as it passes through. But with time, this area becomes dusty, conducive to the growth of germs and mold, and emits foul aromas. Over time, the interior unit will get frozen, with thick ice adhering to the louvers and holes and restricting airflow.

Faulty Electrical Systems

The circuit is in charge of regulating the functioning of the whole system; if the circuit or other electrical parts fail, the air conditioner will not function. Users should thus examine the circuit, the capacitor, and other components to determine the precise cause.

Problem with Cooling Fan

Your car’s air conditioning system may stop working when it’s hot outside for a variety of reasons, one of which is a cooling fan issue. The following factors might be at blame if the blower is turned on but is weak or not cool: shorted-circuit fan motor, defective capacitor, harmed contactor coil, or damaged electrical circuit

What to Do If Your Car AC Fails In Hot Weather?

Here are some things you can do if the case happen.

Clean and Change the Air Conditioner’s Regularly

Filters that are dirty will restrict the flow of air, which will impede the air conditioner’s ability to cool. Users should thus be mindful of routine cleaning to guarantee efficient device performance. Drivers may think about changing the air filter with a new one if there is an excessive buildup of dirt.

Based on operational circumstances and manufacturer guidelines, the replacement interval should be determined. Typically, car owners should change their air filter with a new one after 16,000 to 24,000 kilometers.

Drive Less in Hot Weather

You should avoid driving during the warmest parts of the day while it’s hot outdoors to save your AC system from stress.

Check The Whole AC System

Drivers should bring their cars to a dealer so that a specialist may examine every component and determine the problem’s root, fixing the issue that causes the car’s air conditioning to malfunction in hot weather.

To guarantee that the device’s operability is restored, the interior components also require a thorough cleaning. If a broken compressor is the root of your air conditioner’s inability to cool, you must fix or replace it. The kind of car and the air conditioner compressor’s manufacturer determine how much it will cost to replace the old one.

Routine Maintenance

An essential treatment for the condition of the car air conditioner not cooling is routine maintenance, particularly when the vehicle must frequently operate in a dusty area. Once a year, drivers should do maintenance on it to inspect and repair any damage.

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How to Maintain Your Car’s Air Conditioner


What you can do for car a/c maintenance and what should be left to a trained professional? Our car air conditioners become more important as summertime approaches, especially in the southern regions where the humidity may occasionally be intolerable.

Most people with a little mechanical skill can complete a few visual inspections and a few manual operations. Here are a few tips to ensure you know your air conditioner is prepared to combat the summertime heat on the road.

Checking The A/C System And Maintaining It

During the months when air conditioning isn’t available, cars operating in cooler northern areas need to operate their air conditioners for roughly 10 minutes each time. By circulating the oil throughout the system, this will keep the seals lubricated and stop them from drying out (which would cause the Freon to leak out.) Additionally, regular use of the air conditioner will help to dry up the air chambers and lessen the possibility of mold and fungus forming there and producing foul odors (or worse). Read : no air conditioning car

In addition to just operating the system on a regular basis, you should examine your air conditioner to catch issues early. Just almost everyone can perform this. The A/C condenser, which is situated in front of the radiator, is where we begin our under-the-hood investigation.

Freon is converted from a gas to a liquid in the condenser (it condenses). Anything that may prevent air from passing through the condenser, like a clogged insect screen, must be removed. The efficiency of the air conditioner will decrease if the condenser is constrained. With a garden hose fitted with a high-pressure nozzle, the condenser is simple to clean.

Engine Fan and Fan Belt Inspection

Checking the engine fan, which might be mechanical or electrical, is the next thing on our list. When an air conditioner is turned on, any electric cooling fan that is installed to the radiator must always be working.

If the fan is not working, the system may experience abnormally high pressures that can break system hoses and leak Freon and oil. This can happen if the fan is not functioning. One electric fan only has to be operating when the air conditioning system is on in certain systems that have two of them.

When you are driving your car and notice that the cold air coming from the air ducts rises significantly when the engine is idle, it is likely the cooling fan is not working.

If you have a mechanical clutch fan with a thermostat in the center, the air is supposed to tighten up and spin faster as it goes past the condenser and the radiator warms up. You may do a quick test to check the condition of the fan clutch.

Reach inside and manually turn the fan while the engine is still cold and off. The fan ought to rotate freely, and that is exactly what it ought to do. As you rotate the engine, you should encounter resistance or drag.

You probably have a faulty fan clutch if it is loose and spins freely while the engine is heated. As mentioned in the previous sentence, if the air coming from the air ducts is chilly when driving but heats up significantly when the car is idling, you probably have a bad clutch fan.

The next step is to visually inspect the fan belt. Look for fractures on the belt’s underside. If cracks are discovered, the belt has to be changed. To avoid applying too much pressure to the components being driven by the belt on older automobiles, a belt tension gauge is required while changing the belt.

These driven things may prematurely fail as a result of this, but this is not an issue with more recent cars since they have spring-loaded belt tensioners that apply the proper amount of tension to the belt.

Checking Operation

Start the engine, set the fan speed switch to the maximum setting, and the temperature control to the coldest setting. A clutch that will engage to spin the internal components is located on the front of the air conditioner compressor. You should be able to drive pulley turning together and see the clutch if you take a close look at the compressor. It is common for the clutch to turn on and off around every 20 to 30 seconds. When the clutch abruptly turns on and off every few seconds, the system likely needs more Freon.

What You Do Need A Professional For

10% to 15% of the Freon in air conditioning systems might be lost annually, well, this is where you should get a qualified expert’s assistance. There is a specific amount of Freon that has to be in every air conditioning system. Typically, a tag may be found on the radiator housing’s top, the hood’s bottom, or the chamber housing the system evaporator.

For the system to operate effectively and properly, the kind and required quantity of Freon are listed on this tag in pounds and ounces. Because oil is carried along when freon leaks, you can frequently see the leak when it occurs. A leak is likely present if greasy or black residue is visible on fittings or hoses. Other methods of locating leaks include using an electrical leak detector or a dye that detects leaks.

It is not a good idea to just add more Freon to a system if it is only low on it. There is no way to determine how much Freon is already in a system, and if too much is added, the compressor might be harmed or excessively high pressure could lead to hose ruptures. The proper approach to recharge an air conditioner is to empty it completely, start over, and add the precise amount specified on the tag described before.

DIY Recharge Kits?

The DIY recharge kits available at most parts stores should be avoided. You must keep in mind that an air conditioner may not be functioning for other reasons besides the depletion of Freon.

What would happen if the system’s issues weren’t caused by low Freon alone? The compressor may be destroyed if Freon is introduced to an already-full system because liquid Freon will enter it, or the system hoses may rupture. That is all not good.

Is Dripping Water A Sign?

You can see water dripping from the vehicle’s undercarriage while the air conditioning system is running. This is completely normal and is condensation from the evaporator that has been removed from the passenger compartment.

Water running in on the passenger-side floor rather than beneath the car is a sign that the condensation drains could be blocked. Where water has been standing for a while, fungus and mold might develop, which can clog the drain port or the hose leading outside. Most of the time, the vehicle’s undercarriage will need to be cleansed of this.

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How to Repair Automotive A/C


Step 1: Check the freon


To check the pressure of your freon, you will need a set of manifold gauges.

Here are some general recommendations for the pressures and temperatures of an air conditioning system dependent on the outside temperature. As a general rule, keep in mind that your real temperatures and pressures will fluctuate based on the air’s humidity level and the state of your system.

It is a good idea to keep a water hose close by and spray water on the air conditioner condenser when checking the freon level while the car is running at idle. In front of the radiator is where you’ll find the condenser. Read : Why is my ac not blowing air in my car

For vehicles currently running with freon R-134a only:

Outside Lowside Highside Center Vent Temp
90F 35-40 psi 190-225 psi 44-50 F
80F 30-40 psi 190-220 psi 43-48 F
70F 30-40 psi 190-220 psi 44-48 F
60F 28-38 psi 130-190 psi 44-46 F
120F 55-65 psi 320-350 psi 70-75 F
110F 50-60 psi 250-300 psi 68-74 F
100F 40-50 psi 200-250 psi 52-60 F


Run the fan on High, leave all windows open, and rev the engine to 1500 rpm when using R134a. The outside air temperature in degrees Fahrenheit should be between 2.2 and 2.5 times the high side pressure in PSI. For instance, if it’s 90 degrees Fahrenheit, the high side shouldn’t exceed 225 PSI.

Here is a helpful discussion for troubleshooting systems that use freon R-134a.

Problem: Compressor discharge pressure is low.


  1. System leak
  2. Faulty expansion valve
  3. The suction valve is shut
  4. Freon deficiency
  5. A receiver dryer with a plug
  6. Leaking compressor suction valve
  7. Defective compressor reed valves


  1. Fix system leak
  2. Replace valve
  3. Turn on valve
  4. Add freon
  5. Replace the dryer, and
  6. Replace the valve.
  7. Change the reed valves

Problem: Compressor Discharge Pressure at a High Level


  1. Air in the system
  2. a clogged condenser, and
  3. a blocked discharge valve
  4. Overcharged system
  5. Not enough condenser air
  6. A slack fan belt
  7. Condenser is too far from the radiator or not centered on the fan.


  1. Do system recharge
  2. Do condenser clean up
  3. Get the valve open
  4. Remove some of the refrigerant
  5. Install sizable fan
  6. Adjust the fan belt.
  7. Center and measure the distance.

Problem: Suction Pressure Is Low


  1. A lack of refrigerants
  2. A damaged compressor piston
  3. A leaky compressor head gasket
  4. Hose that is bent or flattened
  5. Leaking compressor suction valve
  6. Trash in the expansion valve or screen
  7. Moisture in the system


  1. Give additional refrigerant
  2. Replace the compressor
  3. Also replace the head gasket
  4. Change the hose.
  5. Alter the valve plate
  6. Replace the dryer
  7. Replace the dryer

Problem: Suction Pressure is High


  1. An inadequate expansion valve
  2. Overcharged system
  3. A jammed expansion valve
  4. Reed valves on compressors
  5. A compressor’s head gasket leak


  1. Get the valve tightened
  2. Remove some of the refrigerant
  3. Replace the expansion valve
  4. Change the reed valves.
  5. Change the head gasket

Problem: Compressor not functioning

  1. A faulty belt
  2. A damaged clutch wire or a lack of 12 volts
  3. Damaged piston in a compressor
  4. thermostat defect
  5. Defective clutch coil
  6. Low pressure switch has turned off clutch power due to low refrigerant.


  1. Change the belt
  2. Check for electricity or fix the wiring
  3. Change the compressor
  4. Change the thermostat
  5. Change the clutch coil
  6. give additional refrigerant

Problem: Evaporator Isn’t Cooling


  1. frozen coil; high switch setting
  2. slipping drive belt
  3. hot air leaks
  4. The receiver dryer is plugged
  5. Broken capillary tube
  6. Low refrigerant levels
  7. High head pressure
  8. Suction pressure is low
  9. Suction pressure is high
  10. A faulty expansion valve
  11. Freezing of the expansion valve


  1. Reverse the thermostat.
  2. Adjust the belt
  3. Look for vents or holes.
  4. Change the dryer
  5. Change the expansion valve
  6. Give additional refrigerant
  7. already explained above
  8. already explained above
  9. already explained above
  10. Change the expansion valve
  11. Remove and replace the dryer

Step 2: Flushing and Expantion Valve

You will need to remove the expansion valve, drier, and the compressor if you determine that the A/C system has to be cleansed to get rid of dirt and oils. PLEASE DO NOT FLUSH THROUGH THESE PARTS. Additionally, as oils often do not mix well, if you are retrofitting your system from R-12, you will need to drain off all the old mineral oil. Mixing oils or refrigerants will cause what mechanics refer to as “the black death.”


You can discover the evaporator to be exceedingly unclean once you’ve taken it out of the car. Remember to be extremely careful not to get water in the pipes that the freon runs through when cleaning your mines in the shower.

It wouldn’t be a terrible idea to repair the expansion valve and do your best to wrap it in some thermal insulation material if you had previously spent all that time pulling it out of the car. To keep it in place, I used tape and some packaging material. (On second thought, perhaps glue would have been a better choice.)

The process of flushing All you need to do is spray an AC cleansing substance into the freon pipes, which I won’t go into detail about. After waiting 20 minutes, blow shop air over it to clean it out. I had the good fortune to have access to my school’s shop compressor. You will probably have to wait for the tank to replenish if you use a potable one because it won’t be able to keep up with demand.

Step 3: Vacuuming

Every time the air conditioning system has been opened or pressure has dropped, it is crucial to replace the dryer. Due to the fact that the dryer absorbs any moisture that may have entered the system. Make careful to drain the oil from the old dryer before adding the equal quantity of new oil to the new dryer when installing a new one. Since the dryer loses its effectiveness after about two hours outside, do this shortly before cleaning.

It is now time to perform a vacuum. If you tend to use general purpose vacuum pump and it does not fit the manifold gauge hoses, then you might want to consider visiting your neighborhood a/c supply store where, more often than not, you may get the correct fitting at a reasonable price. If you already have an air compressor, you might want to consider an air-powered vacuum pump, which costs less than $50, as electric pumps can cost up to $200.

You must remove air and moisture from the system after the vacuum pump is attached. It is advised to carry out this action when the temperature is greater than 80 degrees. So, if at all possible, try to avoid doing it in the dead of winter. Allow a vacuum pump to operate for 20 minutes when it has achieved almost 30 in/Hg (inches of mercury), then turn it off.

Turn on the pump to remove the water if the vacuum begins to drop somewhat since this indicates that some water has evaporated. After that, let the vacuum sit for at least 45 minutes. If the pressure cannot be maintained, a leak somewhere in the system must exist. Before adding more fluid, make sure to fix it.

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