The air conditioner system is intricate and runs mostly independently of the engine and the rest of the car. That said, manufacturers will build it such that one component performs several functions wherever feasible to save manufacturing costs, as with the radiator fan.
The radiator fan also serves as the condenser fan, so it should always be on while the air conditioner runs. In front of the coolant radiator, there is a second, smaller radiator called the condenser, which is used to lower the temperature of the high-pressure refrigerant. Yet even while the car is at a stop, the fan keeps air flowing into the condenser.
How Does the AC Work?
It would be helpful if we understood how the AC system works before further exploring why the radiator must run while the AC is turned on. The AC compressor receives low-pressure refrigerant in a gaseous form to begin the whole process. When the compressor completes its task, the refrigerant exits in a high-pressure gas form and travels to the condenser (AC radiator).
The refrigerant is sufficiently cooled within the condenser to turn it into a liquid. The refrigerant then passes via an expansion valve, where a pressure decrease causes it to cool immediately. The evaporator, located inside the dashboard, is the final stop. The evaporator is a radiator as well, although it works somewhat differently.
The refrigerant temperature decreases dramatically due to the evaporator’s conversion of the refrigerant into a gas. As soon as the refrigerant temperature begins to fall, it absorbs the heat from the evaporator, and the air circulates through it, cooling the evaporator walls and the blower air.
Why Does the Radiator Fan Need to Be On?
As of now, we are aware that the condenser functions similarly to every other cooling radiator. And the method to do so is to provide airflow, which removes heat and cools whatever is passing through—in this instance, refrigerant—whether it be coolant or another kind of fluid. However, the refrigerant in the AC system requires airflow as soon as the AC is turned on, unlike the coolant, which does not need it until the engine has warmed up.
The refrigerant must be cooled by pulling air through the condenser while your car is stationary, so a fan is required. The radiator behind the condenser will draw air through the radiator and the condenser since they are adjacent. Therefore the same fan may be used for both. And since the car is immobile while the AC is turned on, the fan must always work.
But, as you start to drive and achieve a sufficient speed, the fan should stop since the natural airflow is sufficient to cool the condenser. Of course, the outside air temperature must also be included in this calculation, but you get the idea.
To verify whether your radiator fans are functioning, switch on the AC when the engine is cold, and the car is standing. But bear in mind that some cars have two fans, and in this situation, normally just one turns on, so do not freak out if you only see one running.
However, remember that it is not always necessary for the fan to run since your temperature settings and the ambient temperature might influence whether or not it does. Also, the fan will not operate if any other AC parts, such as the compressor clutch, are broken.
What Happens If the Radiator Fan Is Not Turned On?
Below, we will discuss what occurs within the AC system and the apparent issues a damaged radiator fan can cause (namely, engine overheating under certain circumstances). If the condenser’s cooling is inadequate due to a damaged fan, the refrigerant pressure will increase quickly throughout the system.
Naturally, the AC pipes, the condenser, the evaporator, etc., will fracture if the pressure increases enough. But fortunately, it nearly never occurs as the AC system is equipped with a pressure sensor that will turn off the compressor when it detects an excessive rise in refrigerant pressure.
It implies that in addition to the evident absence of whirling fan sounds, you will notice your AC sporadically going on and off before it resumes regular operation once you begin driving. But if the fan does not start, it does not always indicate broken.
Reasons for a Faulty Radiator Fan
Blown Fuse
Checking the fuse should be your first step if your radiator fan never turns on. Locate the radiator fan fuse using your owner’s handbook, then check whether it is burned out. The engine bay fuse box is usually where the fuse is located.
Faulty Fan Relay
In effect, the radiator fan relay functions as a remote switch. The ECU and the AC compressor send signals to the relay through a signal line, instructing it to turn on the fan. Unfortunately, the fan will not operate if the relay is broken. The fan relay should be located using your owner’s handbook once again, and it should then be examined.
Also, you may leave the relay plugged in, start the engine, and then switch on the air conditioning to hear whether a click is coming from it. If you do, the relay is effective. If not, you may just replace it with a new one without doing any additional testing.
Broken Wires
Most of the time, the wires leading from the radiator fan are very visible and short, making it simple to check them. Breaks in the wires or indications of heat damage, in addition to burning indicators, are what you are searching for. If you come across any of the three, cut the broken wire pieces out and replace them with new ones that include wire connections and insulation provided by heat shrink tubes.
Faulty Fan
The radiator fan might malfunction, whether mechanical or electric, which happens often. Even if you drive a modest 1990s hatchback, the fan will cost you at least $80-$120, so having it checked out at a reliable repair facility is a good idea before investing in a new one.
Faulty AC System
Last but not least, if you see that the fan activates when the engine temperature rises but not when the AC is turned on, you are probably dealing with a malfunctioning AC system component. It might be a faulty AC compressor, clutch, a low or overcharged refrigerant, etc. You should always take your car in for an AC system check.
Why Do My Radiator Fans Only Run When The AC Is On?
The radiator fan must also turn on the air conditioner to work. The only other time the fan should turn is when the engine begins to overheat, but that only occurs in stop-and-go traffic or during hot weather, which is another reason it only operates while the AC is on. In conclusion, this is normal if your engine is not overheated.
When Should the Radiator Fan Start Running?
About 90C or 195F is the average working temperature for coolant. The temperature at which the radiator fan activates is around 95C or over 200F; however, specific temperatures vary across automobiles and engines.
Why does the radiator fan turn on?
The radiator fan is activated by either the AC compressor or the coolant fan switch. The coolant fan switch keeps track of the coolant’s temperature as it flows back into the engine and is located in one of the radiator’s bottom hoses. The switch starts the radiator fan when the temperature rises too much. Moreover, the radiator fan is also activated each time the AC compressor starts up.
Does the Thermostat Regulate the Radiator Fan?
No, the radiator fan is not controlled by the thermostat. The thermostat is a mechanical valve that permits coolant to flow through the radiator as the temperature increases around it. A separate switch located in the lower radiator hose is used to regulate the radiator fan.
What Does a Car’s AC Fan Do?
An automobile’s air conditioning fan draws air through the condenser (AC radiator) like a radiator fan. Nevertheless, not all automobiles have it since the coolant radiator fan also serves as the AC fan in most vehicles.
How Low Can AC Refrigerant Go Without a Leak?
True, but not by much. AC refrigerant may run low without a leak. In hotter areas, the AC system should be recharged once a year, every two or three years. But once again, there will not be the much-lost refrigerant.
What Signs Point to a Faulty AC Compressor?
The major signs of a faulty AC compressor include hot air flowing, the AC not working or turning off after you turn it on, and the compressor sounds like grinding or buzzing.
What Happens If I Overcharge My Car’s AC?
If you overload the AC system, there will be excessively high refrigerant pressure. This will result in the AC randomly switching off, the AC compressor failing, and hot air pouring into the cabin. Avoid using the AC if you think it may be overcharged, and have it repaired as soon as you can.
Conclusion
Now that we understand how the AC system works, we can see that the condenser (AC radiator) needs a steady airflow. We also know that the radiator fan must turn on in conjunction with the AC since it is the radiator fan that forces air through the condenser. It clearly indicates a problem with the radiator fan if it does not turn on while the AC is running.