Have you ever wondered what happens inside your air conditioner? If so, then you should read this article because today I will delve into the connections and components that drive your air conditioner.

We will take a look at the diagrams of the indoor and outdoor units of an air conditioner, and then we will discuss the components on the indoor unit’s PCB, as all the intelligent work is done here.

So, let’s dive right into it.

It’s important to find cheaper PCBA manufacturers to order these boards at an affordable price.

Before we begin, you’ll need to manufacture 10 high-quality PCBs at a cheap price and have them delivered to your doorstep. I won’t go into too much detail about PCBA manufacturers here.

How Air Conditioning Works

Air conditioners function by collecting warm air from the room, passing it through coils and refrigerant, and then releasing the cold air back into the space it came from. This is the fundamental principle behind all air conditioning units.

When you turn on the air conditioner and set the desired temperature (e.g. 20 degrees Celsius), the room temperature sensor inside the unit detects the room’s temperature and compares it with the temperature you have chosen.

Warm air is drawn through the indoor unit’s grille and flows through a set of tubes or coils in which the refrigerant flows. The refrigerant absorbs heat and converts into a hot gas, thus removing heat from the air passing over the evaporator coil. Note that the evaporator coil not only absorbs heat but also extracts moisture from the incoming air, helping to reduce the humidity in the room.

The hot refrigerant gas is then conveyed to the compressor located inside the outdoor unit. As its name suggests, the compressor compresses the gas, making it hot, because compressing a gas increases its temperature. This hot, high-pressure gas then moves to the condenser, which is the third component of the system. Here, the hot gas is condensed into a liquid. Although the refrigerant enters the condenser as a hot gas, it quickly becomes a cooler liquid as the heat from the hot gas dissipates through metal fins to the surrounding environment. Therefore, when the refrigerant leaves the condenser, it has lost heat and has become a cooler liquid. It flows through an expansion valve, which is a small hole in the copper tubing of the system that controls the flow of cold liquid refrigerant into the evaporator, thus enabling the refrigerant to start its journey again.

This process is repeated until the desired temperature is attained. To put it simply, air conditioning units continue to draw in warm air and release it back into the room until there is no more warm air left to cool.

What components does the air conditioner PCB contain?

When examining the circuitry of an air conditioner’s indoor unit, the following main PCB components are observed:

  • Wiring:

There are three wires inside the indoor unit, used for the live wire, neutral wire, and ground wire respectively. As the outdoor unit lacks a direct power source, the power supply for both the indoor and outdoor units is provided through these wires.

  • Fan capacitor:

An indoor unit fan circulates cool air by blowing air in and out. To power the fan motor, a fan capacitor is needed. Typically, cylindrical dual-run capacitors with a value of about 2uF are used to assist in starting the compressor and condenser fan motors.

  • Microcontroller:

These components function as the air conditioner’s “brain,” acting as decision-making units, control units that oversee motor operation and power transmission, and more. The microcontroller is responsible for turning the compressor on or off according to temperature readings.

  • Temperature sensor:

Two sensors inside the air conditioner indoor unit are employed to detect the temperature of the room and coil respectively. The microcontroller makes the decision of whether to turn the compressor on or off based on the temperature detected by these two sensors and the user’s temperature settings.

  • Power supply unit:

As microcontrollers operate on DC voltage, a power supply unit is required to convert the high-magnitude input AC voltage into a lower magnitude DC voltage and provide it to the microcontroller. The input voltage is commonly 220V AC.

  • Relay:

A power relay connects the indoor unit to the outdoor unit and serves as a switch between them, determining whether the compressor on the outdoor unit is on or off.

In addition to these main components, other crucial components on the air conditioner indoor unit’s circuit board include an explosion-proof rheostat, display, and infrared receiver components. The display indicates the user’s temperature settings, while the infrared receiver component receives commands sent from the infrared remote control. A servo motor also exists to control the AC’s blades and direct the airflow.

Some common problems with air conditioners.

problems with air conditioners.

Motor running capacitor burnt out:

In this scenario, the motor running capacitor responsible for driving the indoor unit’s blower motor may burn out. This will cause the blower motor to either not start or move very slowly, resulting in inadequate airflow and insufficient cooling of the room.

Starting capacitor in outdoor unit burnt out:

In this scenario, the starting capacitor used to start the compressor in the outdoor unit may burn out or malfunction. This will cause the compressor to not start, ultimately resulting in insufficient cooling of the room from the indoor unit. If this problem is not addressed promptly, it may cause other components to overheat and become damaged.

Compressor shutting off even when the room is not cool enough:

While not a major issue, sometimes the temperature sensor in the indoor unit may come into contact with coils that are much cooler than the room temperature. When these readings are sent to the microcontroller, it may mistakenly believe that the room is cool enough and shut off the compressor.

read more

Precautions for air conditioner PCB maintenance