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We rarely give any thought to the heating and air conditioning systems in our cars until they stop working. These systems help keep the cabin of the vehicle warm in winter and cool in summer. Maintaining the heating and air conditioning system is key to a comfortable ride, regardless of the season.
While the major function of these systems is for the comfort of the passengers, they are also integral to the defroster system, which keeps the windshield clear and ensures good visibility on a cold or snowy day. Driving with reduced visibility can greatly increase the odds of an accident.
The heating system in a car consists of a number of components. The heater core, heater hoses, heater control valve, blower fan/motor, and the control panel in the cabin are the key parts of the system. The heater core is a like a small radiator mounted under the dash. It has an inlet and outlet to allow the flow of coolant through the core, the heater control valve regulates the amount of hot engine coolant that goes through the heater core. Finally, the heat generated by the heater core is blown into the cabin by the blower motor, which is controlled by the control panel in the cabin.
The air conditioning system uses a compressor, condenser, evaporator and an expansion valve. Refrigerant (R-134a or HFC-134a), is compressed in the compressor system which transforms it into a hot gas. The hot gas is then cooled to a liquid state in the condenser and sent to the expansion valve. When the gas is forced through the expansion valve, it returns to a gas state, which is rapidly cooled in the evaporator. The blower fan blows over the evaporator and sends the cold air into the cabin via the vents. This system is controlled by the control panel in the cabin.
Low Coolant Levels: The hot air that comes into the vehicle is a byproduct of the heat of the coolant in the engine. If the coolant levels are low or the fluid is contaminated, it can lead to a poorly functioning heating system. In most cases a leak is to blame.
Blown Fuse: While a blown fuse can be a quick fix when it comes to the heating system, in most cases it is just a symptom of a larger problem. If the same fuse continues to blow on regular basis the vehicles heating system should be inspected for a bigger issue.
Bad Heater Core: The heater core is basically a mini radiator located behind the dashboard. There are a number of things that can cause a heating core to malfunction, it may be clogged due to contaminants in the anti-freeze. Hoses can crack, leak or become loose. The control valve can also get stuck. A bad heater core will result in zero heat.
Air Pockets in the Heater Core or Hoses: If there is air in the cooling system in most cases there will also be a leak. Air in the system can create air pockets that will interrupt the flow of coolant through the heater core. The air can be bled from the system to resolve this issue.
Malfunctioning Thermostat: The thermostat functions as a shut-off valve between the radiator and the engine. The thermostat is closed as the car warms up. When the engine is warm, the thermostat opens to circulate the anti-freeze. A malfunctioning thermostat will often stick open, resulting in an engine that doesn’t warm up so the heating system doesn’t have enough hot air to warm the cabin.
Bad Blower: The electric blower motor pushes the hot air out into the cabin and if it is malfunctioning the heat will not make it into the vehicle cabin. A bad blower can be caused by a blown fuse, a blower speed controller that is not working properly or the motor itself may be shot.
Loss of Refrigerant: If the air is no longer coming out cold, this could indicate that the refrigerant needs to be recharged or there is a leak in the system. Refrigerant problems are one of the most common reasons an air conditioning system isn’t working properly. The system will need to be recharged from time to time with new refrigerant, as it loses roughly 15 percent every year. A leak can also cause this problem as the system loses refrigerant at the leak site.
Bad Compressor: The compressor works very hard and they run hot due to the internal pressure they must produce. All of this hard work means that a failing compressor is a very common problem with a vehicles air conditioning system. A loud knocking or squealing noise will often point to compressor problems, as will a lack of cold air or the air conditioning just not working at all. This should be repaired immediately as it can affect other parts and run up the cost of the repair.
Leaking Hoses: The air conditioning system relies on a variety of hoses and if they are loose or leaking you could experience a loss of cooling due to leaking refrigerant. Leaking hoses should be replaced as soon as possible.
Failing Condenser: If the air conditioning system is not cooling or just stops working, it could be a condenser problem. In most cases there are two common causes of condenser failure. One is a leak, a condenser has a number of tubes and seals, which can leak, due to normal wear and tear. Unfortunately, these cannot be replaced or repaired so the condenser will have to be replaced. A blockage is the second most common cause of condenser failure. Metallic debris, often from a failing compressor is usually the cause. If this is the case, both the condenser and compressor will have to be replaced.
Failing Condenser Fan: The condenser fan removes the heat generated by the condenser and if it is failing the air conditioning system will not be able to cool. A lack of cooling or a completely non-functioning air conditioning system are common symptoms of this problem. In most cases the fan will have to be replaced.
Faulty Low Pressure Cutout Switch: The low pressure cutout switch prevents the compressor clutch from engaging if the pressure in the system is low, this prevents the compressor from being damaged due to a lack of lubrication. If this is the problem, the air conditioning system will not work at all.
Faulty Blower Motor or Resistor: The blower motor circulates the cold air into the cabin of the car. If the air conditioning system makes noise when you turn it on but no air comes through the vents or if the blower is only operating at full speed the blower motor or resistor could be defective. It is also possible that the fuses that service it are blown.
Faulty Switches: If the air conditioning only works intermittently or you have to jiggle the switches to get it to function there could be a problem with the control panel.
Damaged Receiver/Dryer: If the air conditioner is not blowing out cold air and moisture is accumulating on the windows, there is a good chance the receiver needs to be replaced. This issue should be fixed quickly as the excess moisture could easily damage other air conditioning parts.
Blown Fuse: In some cases, the simplest explanation is the correct one. There are a number of fuses connected to the air conditioning system and if one of them is blown it can shut down the entire system.
A top-rated mobile mechanic will come to your home or office to determine the source and cause of the heating or air conditioning issue, and will then provide a detailed inspection report that includes the scope and cost of the necessary repairs.
While driving around without a proper functioning heating and air conditioning system will certainly be uncomfortable, it is usually not a life or death situation. However, if the defroster is no longer working, this can result in reduced visibility, which can lead to dangerous driving conditions. In most cases, a malfunctioning heating and air conditioning system should be repaired as soon as possible.