Driving during the summer, air conditioning helps fight the heat. As is the case with any mechanical system, a vehicle’s A/C can malfunction from time to time due to individual component failure.
Read on to find out some of the most common reasons behind a car A/C not blowing cold air anymore and how much it is going to cost to fix the issue.
Causes of a Car A/C Not Blowing Cold Air
The following are several of the most common reasons behind blowing inefficiencies within an A/C system.
#1. Low Refrigerant.
Low refrigerant is by far the single most common cause of bad A/C cooling. A low refrigerant level typically results from a leak somewhere in the system that likely went previously undetected.
Regardless, the unfixable leak has to be found and repaired (at all costs) before the A/C system can be recharged.
#2. Excessive Refrigerant.
Excess refrigerant is not as common as low refrigerant, but it can certainly impede the function and ability of an A/C system. The reason for excessive pressures usually is due to the motorist having excessive refrigerant added to their A/C system.
This usually occurs when a motorist adds refrigerant to their A/C system with a charging kit from home.
#3. A/C System Restrictions.
An A/C system may also have restrictions in the system that cause the poor cooling. Restrictions will stop refrigerant flow and may lead to pressures that you did not expect to see. If there are restrictions in the A/C system you can likely expect the refrigerant to not cool.
#4. Air/Moisture Contamination.
Air or moisture contamination must be eliminated from a vehicle’s A/C system to ensure maximum efficiency. The presence of any air or moisture will cause pressure fluctuations in an A/C system.
Air is often unknowingly introduced into the system using an at-home charging kit, and excess moisture contaminates the system by damaging the desiccant material located in the receiver/drier or accumulator.
#5. Internal Compressor Failure.
A compressor is responsible for pressurizing the refrigerant in the A/C system and can easily fail when deprived of oil. Once this happens, the cooling stops immediately, and the temperature of the car’s cabin will begin to rise.
After experiencing an internal failure of an A/C compressor, one must flush the rest of the A/C system.
#6. Clutch Failure.
The compressor of an A/C system uses a clutch as an engagement mechanism to run the rest of the internal components of the compressor. The clutch is magnetically actuated and, when disengaged, returns to the freewheeling position.
If an A/C clutch should fail, the compressor can never be engaged.
#7. Faulty Cooling Fan.
A faulty cooling fan can also limit cooling efficiency. The condenser requires adequate airflow at all times to keep high-side pressures in check.
If air-conditioning is not blowing cold air when idle but will engage and function appropriately when the vehicle receives a sufficient RPM (engine speed), it is almost always a faulty cooling fan.
#8. Malfunctioning Sensors.
The failure of any of an A/C system’s numerous sensors will negatively affect the operation of the A/C system. The vehicle’s computer will struggle to initiate the proper compressor clutch duty cycles.
How Much Will It Cost to Repair?
The cost of repairing an A/C system can vary greatly, depending on the failure type. The retail price of a component of an A/C system can also be very different from one make/model to another.
Typically, putting it in the middle, you might expect to pay in the range of $150-$300 to recharge your A/C system with refrigerant.
This is assuming no major system leak is present, and that your refrigerant layers have only reduced due to loss over multiple years.
At the other end of the spectrum, you may expect to pay considerably more if the A/C compressor had an internal failure. If this occurs, the system has to be flushed prior to installing the new compressor.
You would also replace the system’s metering device and receiver/dryer (or accumulator). Including labor, an average job like this costs around $500-$1,100.
How a Car Air Conditioning System Works
A vehicle’s A/C system cools cabin air by circulating refrigerant through a closed loop of various physical states. Each of these physical state changes directly relates to temperature/pressure changes in the system.
It is important to maintain a vehicle’s A/C system with the proper amount of refrigerant, and not allowing air from the atmosphere to mix with the refrigerant.
Main Parts of a Car AC
A car air conditioning system is also still only able to function properly with a number of parts, each of which serves a specific purpose. These parts, with general definition are below.
#1. A/C Compressor.
The A/C compressor is the device that pressurizes and circulates the refrigerant through the system. The A/C compressor has a magnetic clutch that engages when required by switched input or electronic request.
#2. Condenser.
An A/C system’s condenser is a thin, radiator looking device that is mounted behind the vehicle’s grill. As air is passed over the condenser, the refrigerant state changes from gas to liquid, losing heat in the process.
#3. Dryer/Accumulator.
Depending on what style of A/C system is present in the vehicle, it has either an accumulator or receiver dryer. The accumulator is found in orifice tube A/C systems, while the receiver dryer is present in expansion valve A/C systems.
These devices contain industrial desiccant that absorbs moisture that may have entered the system.
#4. Metering Device (Orifice Tube/Expansion Valve).
All automotive A/C systems utilize a metering device to control refrigerant flow into the evaporator.
Typically, an orifice tube is used to make this determination in some systems, while other systems use a metering expansion valve. The location of metering device will vary depending on a system’s design.
#5. Evaporator Core.
Evaporator cores (heat exchangers) are located inside the vehicle beneath the dash. The refrigerant that has passed through the vehicle condenser and has changed state from liquid to vapor as the refrigerant absorbs heat from the interior of the vehicle.
Sensors
In addition to the basic components, an A/C system has a number of sensors that provide important information that the system needs to operate properly. These sensors, and their basic function, are as follows.
#1. Low Pressure Switch.
The low-pressure switch is used to monitor a relative loss of refrigerant and lubricating oil.
If the pressures in the low side of the system falls below a specific value, the low pressure switch trips to disable the compressor to reduce risk of failure.
#2. High Pressure Switch.
The high-pressure switch monitors the over-pressurization of refrigerant in the A/C system.
If, for any reason, the system pressure climbs to a maximum value, the high-pressure switch trips to halt operation of the compressor clutch.
#3. Ambient Temperature Sensor.
It is common for modern automotive A/C systems to have an ambient temperature sensor that senses and relays cabin temperature. This data is processed to optimize cooling and stabilize cabin temperature under various driving conditions.
How to Prevent Future A/C Problems
In some instances, there are A/C system failures that simply cannot be overlooked. However, in other cases, failures can be avoided in significant parts by performing simple service procedures.
Most importantly, your A/C system should be serviced at your vehicle’s specified intervals. For many makes and models, this service interval is usually in the vicinity of 100,000 miles.
A simple A/C service usually involves checking that your system is topped off with refrigerant, and to ensure that there are no obvious leaks.
Before this happens, a service technician will connect a set of gauges to the vehicle’s A/C charging ports and will read the high and low pressures. This allows the technician to assess the system’s charge state.
If these pressures are lower than they should be, then the refrigerant will be topped up, evacuated and recharged, or perhaps the technician will identify and repair a leak. A technician will also access for the source of any offending leaks using a UV light.
Preventative A/C service, as described here, can be very useful when these services are designed to help increase the service life of systems and components of your vehicle’s A/C system.
Services of this nature help prevent your vehicle’s A/C system from running low on refrigerant, which will cause the compressor to keep short-cycling.
Short cycling, day after day, will ultimately enhance the wear to internal components of the A/C compressor and its magnetic clutch assembly.