Most vehicle mechanics think it’s OK but it isn’t
Over-heating is a very common motor vehicle problem. It sometimes makes vehicle owners feel they just want to sell off or even dump their vehicle. The more sober ones run for help from their mechanics but even they do not always get the right diagnosis and treatment. Instead their vehicles are sometimes placed in even more danger.
Over-heating occurs when some parts of an engine are kept running all the time when they possibly should not. This poses great danger to the engine and its other parts could be over stressed and breakdown very fast. Therefore, it is important to observe how the engine’s cooling fan is working. This is because the cooling fan is only needed when the engine temperature rises above a predetermined level or when the engine load is increased on the cooling system for example when you are running your air conditioner. The rest of the time if the fan is running, it would be a waste of electrical energy. So the engine normally turns it off.
Electric cooling fans are found on most front-wheel drive vehicles with transverse mounted engines as well as many late model rear-wheel drive vehicles. Electric fans are used on front wheel drive (FWD) cars because the fan does not require a belt drive and can be mounted independent of the engine’s location. What’s more electric fans require less power to operate to improve the fuel economy and performance because they run much quieter and allow more precise control over the cooling system.
By comparing the electrical fan with the mechanical belt-driven fan, the mechanical belt-driven fan requires 5 to 15 horsepower depending on the engine speed and the size of the fan.
When driving on highways there is usually enough air flow through the radiator. This cool the coolant and so the cooling fan is not required to run because it’s main function is draw air from atmosphere through the radiator to cool the coolant.
The cooling fan is more important when vehicle is in traffic or when cruising at slow speeds. The cooling fan is controlled by a temperature switch located on the radiator or on the engine in older vehicle models. When the temperature of the coolant exceeds the switch temperature rating, the switch closes and energises a relay that switched a voltage to run the fan and it will continues to run until the coolant temperature drops back below the opening point of the switch.
Most electric fans are also wired to come on when the air con is switched on. However many vehicles have a separate fan for the air con condenser called the dual fan system and one or both fans come on when the air con is on. However this type of technology is improved in computerised engine controls. Here the fan operation is regulated by the engine control module.
Input or a signal from the coolant temperature sensor and also the vehicle speed sensor determine when the fan needs to be on and off. Most technicians do not know these circuits and what they resort to is looping the cooling fan direct and run them all the time and as soon as you put on the ignition switch the fans are on. That is not right but can be done as emergency to get off the road to the workshop. Having your cooling fans running all the time has got two major effects that could prove costly.
• The first one is over-cooling an engine is very bad because there is no room or allowance for expansion which results into great wear of, most especially, the engine block and piston rings.
• The battery service life is shortened because the battery is meant to store electrical energy that is used when the engine is not running. When the cooling fans run all time they always drain voltage from the battery as it is charged. This stresses the battery and makes it weaker and weaker.
• The cooling fans too are stressed by the constant running. It wears out the contact brushes and the over-heating of the fan armature which sometimes leads to burning of the field windings.
If your cooling fans are running all time when you turn on the ignition switch then you need to fix it very fast. If not, you could be buying a battery in the next few months. In a worse case, your car will start to smoke due to wear and its fuel consumption will slightly rise
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