04 Radiator Problems Including “Radiator Fan Only Turns on When Ac Is on”


The radiator is one of the most important parts of the car. This article will explain why the radiator fan only turns on when ac is on and more 03 problems.

Your car’s radiator is one of the simplest parts in the car that you don’t care until a problem comes. It is simply cooling down your vehicle’s heat. But, without its utmost function, cooling your engine, your car will not normally work at least a minute. Being one of the problems related with the car’s radiator, “radiator fan only turns on when ac is on”, is something that you need to look on.  Here are more 05 problems and fixes regarding the car’s radiator.

Table of Contents

Leaks With The Radiator Is Common

Leaks are the most common errors found with the radiator. Having fluid under your metal hood is one thing that you have to worry. Although it is not too much with the cost, you will find it costly when you drive without knowing it. Hoses connected to the radiator is the most common cause for having leaks. When it comes to the exact reason for creating the leaks, your car’s fluid circulating pressure is the reason. Keeping the fluid in a higher temperature all the time, and the higher pressure make a possible way to go out of the hoses.

If it is about a loosen hose, you will be able to simply fix it by tightening the loosen end. If it is about a small hall in the hose, you will have to replace the hose which is more expensive than tightening. The best thing to do to avoid unfortunate incidents is to be watchful about the greenish or reddish colored fluids under the car.

Radiator Fan Only Turns on When Ac Is on?

Radiator Fan Only Turns on When Ac Is on?

Although it is not as common as either having leaks or a rusty radiator, you will find it sometimes on your car as well. It is important to identify the functioning of the radiator. You might have been thinking if there is an additional sensor for the radiator other than the cooling sensor as well. Indeed, there is nothing that you need to worry about that. What you have is a bad thermoswitch.

Its main function is to regulate the temperature of the vehicle when the cooling happens in a higher temperature. When the coolant is circulating in a higher temperature, the switch closes the fan to work on the cooling tasks.

The air-conditioning has got the same fans when having the tasks to regulate the temperature in the car’s inner atmosphere, the cabin. It means the exhaust fans work when the temperature is higher in two circumstances. The first one is when the car’s cabin has a higher temperature and the car’s engine has a higher temperature. The thermoswithc’s duty is to manage these two scenarios together. If your car’s radiator fan only turns on when the ac is on, you will have to replace the switch. It important to know that the replacement has to be conducted soon. If the AC doesn’t work properly, your car will be in trouble.

Rusting The Radiator Is Also a Problem

If you observe rust on the car, you will have to be aware that your car’s radiator is rusting. Your car has got lots of things to deal with. The rust is one of those things as a threat. The air, mud, oxidants, gases, and many things are in the atmosphere the radiator has to deal with. When it comes to the radiator, all these things are available in the outside of the radiator.

If your car has got a higher temperature recorded in the dashboard, or getting alerts from the dashboard, you will have to check the radiator for the rust. Also, the best way to observe the rust is the coolant. If you see a brownish color in the coolant, you will have to expect the rust in the radiator as a sure thing. Other than that, coastal drives, cooler climates, heavy rains, and muddy conditions will cause you to worry about ruts more than in typical areas with smooth roads.

Overheating Radiator When Idling

Being one of the faults associated with the radiator, you might have a chance of observing the heating the engine in the idle.  It will be similar to a radiator fan only turns on when ac is on as well. If you observe the hating of the of the engine as spikes in the traffic or stopping for a moment, that will be the most common symptom. As a modern car owner, you have to be more specific about this issue than anyone else.

There is an electric fan in the modern cars that helps when the car is stopped or in the idling position. Its main duty is to rest the radiator while you are resting the car. When there is an error or a broken part in the vehicle, your car will increase its temperature during the idling. When you start to accelerate the car, the typical cooling process will start as soon as the radiator turns back on.

What to do in this situation?

Simply, you have to look for an answer for this error. The best way to do that is to take your car to a service station. When you are in traffic, you will have to accelerate and increase the RPM for not dropping the radiator at work.


The radiator is as important as the engine. Although it is not as faulty as the other parts in the car, you will have to watch for errors. There is nothing more you can do except looking for rust in the coolant, fluid leaks, and sudden temperature increases.

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