DIY

Car A/C Not Cooling? 5 Reasons Why

Reading Time: 7 minutes

If your vehicle’s air conditioning system isn’t working properly, it’s definitely an inconvenience⁠—especially if you’re driving around during the summer when temperatures can get extremely unbearable. 

There are many possible reasons for your air conditioning to go out, the most common of which are leaks or compressor issues. If your car’s A/C isn’t blowing cold air, you could be looking at anything from a leaking hose to a faulty evaporator core. 

Diagnosing the root cause of A/C problems in your vehicle can be difficult since there are so many possibilities. 

Below, we’ll discuss some of the potential causes for inoperative A/C. 

Man adjusting car's A/C
Diagnosing the root cause of A/C problems in your vehicle can be difficult since there are so many possibilities. 

Why is My Car A/C Not Cooling?

Your vehicle’s A/C system relies on electrical components and other parts so it can perform optimally. Because of the complexity of your A/C system, it will be difficult to pinpoint a definite cause of a problem. 

The issues listed below are just some of the top causes of A/C malfunction. 

If your car A/C is not blowing cold air or just simply not working, then you might be dealing with one or more of the problems listed below. 

A/C Refrigerant is Leaking

The refrigerant is what keeps the cabin cool. When there is a refrigerant leak, an oily substance can form around an A/C hose. These leaks are usually hard to spot but can be detected by UV A/C leak detection kits. 

Cooling Fan Not Working

A vehicle has one or two fans in the A/C system, which are usually located at the front of the vehicle. Fan motors can get worn-out over time and eventually can’t get up to speed. 

In some cases, the problem might also lie with the cooling fan wiring or other parts of the circuit. 

A/C Condenser is Faulty

A bad A/C condenser can definitely affect your vehicle’s cabin cooling capabilities.

The A/C condenser lowers the temperature of the refrigerant and turns it from a gas into a liquid. In order for it to function properly, its fins need to be free of any obstruction that can inhibit airflow. The condenser must also be free of internal obstructions and not have any leaks. 

Since it’s usually located toward the front of the vehicle, you can easily go to the front grille to inspect it for any leaves or other debris that could prevent airflow. Rocks and organic debris can also cause the fins of the condenser to rupture and leak refrigerant.

A/C Compressor Clutch & Clutch Relay Problems

The compressor has a magnetic clutch that needs full battery voltage to engage. The clutch may fail to engage and drive the compressor if the voltage to the clutch is low, if the clutch is bad, or if the air gap in the clutch is too great. 

The clutch relay can also have problems that can be checked by looking at the voltage it receives while the A/C is turned on. If bypassing the relay with a jumper wire or routing the battery voltage directly to the compressor clutch makes the A/C work, the relay is probably faulty. 

Electrical Issues

Is your car A/C blowing warm air intermittently? Other electrical issues with the A/C components may be present. 

The problem can be as simple as a faulty A/C control switch being worn out or problems with the low-pressure cutout switch. This switch prevents the compressor from running if the refrigerant level is low. If this switch is not reading correctly, it can affect how the compressor functions. 

 Sometimes, electric issues in the A/C system are caused by worn-out electrical components or wires that have short-circuited. Fuses can also blow up and affect the whole AC circuitry. 

Man in car with broken A/C
If your vehicle’s air conditioning system isn’t working properly, it’s definitely an inconvenience⁠—especially if you’re driving around during the summer.

Diagnosing Car A/C Problems

Is your car A/C blowing hot air instead of cold air or is it blowing only moderately cool air even when it’s at the highest setting? 

Below are some diagnostic tips and tricks you can try to pinpoint the root cause of your A/C problems.  

Preliminary Check

Is your A/C blowing warm air? Is it set on high but continues to blow only moderately cool air? If this happens, you need to check the following:

  • Check the cooling fan radiator to see if it’s running while the air conditioning is on. 
  • Try to see if there are any obstructions or debris that have been caught in between the fins of the condenser. 

Check your repair manual for the upper and lower limits of the recommended pressure in the system. Using a manifold gauge set, check the system pressure and compare it to the standard.

Compressor Check

If there are no clogs in the system or if the fans are running well, you’ll need to check the A/C compressor next. Run your A/C on its maximum cool and fan settings and make sure that the magnetic clutch engages the compressor. 

There are several outcomes to this test:

  • If the clutch is engaging or disengaging rapidly, the refrigerant level may be low. Use a manifold gauge set to verify. 
  •  If the clutch is not engaging, check the voltage getting to the compressor. If there is voltage, the clutch itself may be faulty or its gap is too wide.
  • If there is no voltage at all, a fuse may have blown out, a cycling switch may be faulty or there’s not enough refrigerant pressure to trigger the low-pressure cut-off switch that cycles the compressor. 
  • Turn the A/C and the vehicle OFF. Rotate the clutch drive plate by hand (you can do this without removing the serpentine belt) to ensure that the compressor turns. If the plate does not move or is hard to turn, the compressor is bad and needs to be replaced. 
Mechanic checking instructions from car manual
When doing preliminary checks on your A/C, it helps to consult your repair manual.

Refrigerant Leak Check

A refrigerant leak is one of the most common causes of a faulty A/C system. Since the A/C system is supposed to be a closed system, a decrease in the refrigerant level indicates that there is a leak. 

Perform the following checks to rule out leaks as the root cause of your A/C cooling problems:

  • Use a UV AC leak detection kit to check for leaks. This method introduces UV dye to the system to help you spot leaks. Though, before you use this method, check to see if it’s compatible with your vehicle’s AC system.
  • Check all the fittings to make sure they’re secure.
  • Check the front seal and the o-rings that seal the pressure switches on the back of some compressors.
  • Check the hose manifolds on the compressor.
  • Check the AC hoses and where they bend onto the fittings.
  • Check the Schrader Valves.
  • Check for holes in the condenser.
  • Check where the evaporator drains condensation with UV light. You might see oil or dye on this component. 

How Do I Fix My Car’s A/C?

Some of the problems and the diagnoses here have a DIY solution. For example, you can replace your cooling fans on your own with a replacement part that’s compatible with your vehicle’s year, make, and model. 

However, although you can probably address some of these problems on your own, you need to remember that whenever the A/C system is opened for service, the refrigerant must always be recovered. This means that as a DIYer, you’ll need to take your car into a shop and have the refrigerant recovered using professional equipment. 

Then, after you’re done performing the repair, you’ll need to return to the shop to have the system recharged. 

In addition, some electrical issues need to be diagnosed and addressed by experienced technicians⁠—this is why many A/C repairs are best left to professionals. 

Car A/C Maintenance Tips

To avoid any of the problems listed above, you need to regularly inspect and maintain your vehicle’s A/C system. 

Here are some quick tips you can follow to make sure your car A/C is always in the best condition:

Regularly Run the A/C

Running the A/C system even during colder months helps maintain the proper gas pressure and keeps the compressor working properly. 

The refrigerant contains lubricating oils, so keeping the A/C system running regularly will help lubricate the seals and other components of the system. 

To do this, run the AC on its highest and coolest setting for 10 minutes each week even if you’re not using the A/C. 

Closeup of car's A/C switch
Some A/C-related problems can be dealt with a DIY solution.

Run Your A/C on Defrost Mode

Putting your A/C on defrost mode eliminates excess moisture and prevents mold and mildew from building up. This process also removes unpleasant odors inside the vehicle. 

Run your A/C on defrost mode for 5 to 10 minutes each week and your vehicle will remain mold-free.

Check the A/C System Regularly for Leaks & Cracks

If you check your vehicle regularly, it’s important to include the A/C system during your checks. This will help you pinpoint problems before they get worse. 

It’s difficult to check for leaks as mentioned above, but keeping an eye out for these problems will definitely help you save on repair or replacement costs. 

Inspect the Cabin Filter 

Cabin filters keep the air inside the vehicle clean. However, they serve a secondary purpose of keeping the evaporator free of dirt and debris as well. These filters are usually located behind the glove box and can be replaced easily. 

Check your repair guide or owner’s manual for the regular service intervals for this part. 

Have Professionals Perform Tests & Recharges

Some procedures and performance tests on your A/C system will require specialized equipment and professional service. It’s recommended that you bring in your vehicle for an A/C performance test regularly to make sure that it is in tip-top shape.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic.

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