Is it worth using universal boards for the air conditioner and their replacement

Universal boards for the air conditioner are used when it is difficult to find a part for the repair of HVAC equipment. There is a large line of models on sale that differ in device and functionality. Chinese-made boards are sold in a wide price range.

Description of cheap model QD-U02B and expensive model QD-U11A

QD-U02B

The devices are powered by an external transformer. The relay for compressor control has a rating of 30 A, for a four-way valve and fans - 5 A. The relay is connected to the working elements with 0.8 * 6.4 mm terminal blocks. A simple microcontroller is enough to receive control signals from temperature and photo sensors.

The receiving board of the cheap model QD-U02B does not have a case and is equipped with indicator LEDs, a control button and a photo module. The dimensions of the device allow it to be installed in conventional wall-mounted models. If it is not possible to insert the board in place of the previous one, each element of the part can be disconnected and sequential installation carried out.

The control panel has a small black screen and few buttons. However, it is sufficient to perform all the functions of the board.

QD-U11A

The expensive model QD-U11A has a separate module in the case. It is equipped with a room temperature indicator. You can manually set the required air temperature. The control has a timer and run indicator. It is connected to the main board by a flexible cable.

The remote control has an attractive appearance, has an informative display and is made of high-quality plastic.

The soldering of the presented boards is of high quality, the tracks are varnished, the power tracks are additionally reinforced with solder. However, the element itself is made of low-quality getinax, so you should be careful during installation.

How does a malfunction of the air conditioner board manifest

When the LEDs on the indoor unit are blinking and it is not possible to turn on the split system, it can be assumed that there has been a failure in the software settings. They are eliminated by reprogramming the control element in the service center using the codes.

Air conditioning circuits often burn out during power surges. Inverter devices are especially sensitive to surges. In such cases, the board needs to be repaired or replaced.

The main malfunctions of the control element and their causes:

• Manufacturers equip control circuits with solid state switches that are responsible for fan operation. If it malfunctions, you can suspect a malfunction of the switches. Before repairing, be sure to check the resistance of the element. If the value is close to zero, the microcircuit must be evaporated.
• Malfunctions in the temperature sensors and compressor also indicate a circuit malfunction.
• If the burned-out microcircuit is visible to the naked eye, you will not have to measure the resistance. The control element is immediately repaired or replaced.
• In some cases, installers make a mistake in interconnect connections, which also causes board burnout. The voltage regulator, transformer and diode bridges often burn out.

If the control element is completely burned out, it must be replaced.

Is it worth using universal boards

General purpose boards are suitable for installation in most air conditioners, however, the scope of their use does not go beyond certain limits:

• They can only be installed in on-off type air conditioners (non-inverter).
• These controls are only applicable for installation in air conditioners with fan motors with additional windings. When controlling the PWM motor, the air conditioner with the universal board will operate at maximum speed. For such cases, damping resistors are purchased.

When the motors of the indoor unit are powered by direct current BLDC, the combined operation of the universal circuit and the air conditioner is not possible. For wall systems, it is better to choose the QD-U03A model.

Differences between expensive and cheap controls:

• The built-in restart function. After turning off the power and then resuming it, the device will continue to work in the previous mode.
• Equipped with evaporator temperature sensor. This element prevents freezing of the internal heat exchanger.
• The presence of a body on which the element is attached.

It is also worth understanding the peculiarities of installing a universal board in an air conditioner.

Element replacement

An instruction manual is supplied with the universal board. It shows how to connect the element to the air conditioner. The instructions contain a detailed diagram. The receiver board, temperature sensor and transformer are connected with standard connectors, so the risk of error is minimal during this operation.

To connect the board with a four-way valve, a compressor and a fan, there are pin-type connectors on the element. A dozen terminals are supplied with the part, as well as transparent insulation for them. In cooling mode, the four-way valve is not energized, so care should be taken when connecting.

The fan motor is connected to the circuit using three relays (for three speeds). They are also connected with 6.2 mm terminals, so they bite off the standard connector and connect these terminals to the fan motor wires. One of them is put on a common wire, neutral. The rest are connected to the relay outputs.

The universal air conditioner control board is designed for operation with motors that have additional winding leads. One of the wires is common, while the others come from the rest of the windings. Lower resistance wires are designed to power the fan when running at maximum speed.

The board has pins labeled according to the fan speed - Hi (high), Low (low) and Med (medium).

The procedure for replacing the control board of a domestic air conditioner:

• Disconnect power to the device.
• Disassemble the case or remove the block cover.
• Pull the element out of the grooves. To do this, you will have to unscrew the screws, disconnect the connectors and wires.
• Replace the part with a new one and assemble the air conditioner module.

All procedures are performed carefully, because if the board is slightly damaged, the device will not work.

Checking the installed board

The receiving module of the board includes a microcircuit, which contains a sensor, an automatic gain control system and filters to suppress interference. The output has the following conclusions:

• food;
• general;
• output.

The connection diagram is simple - through several optional resistors and a power filter capacitor.

The first stage in assessing the performance of an element is to check the connection of parts to each other and to the main board. The receiving microcircuit is checked for the consumed current - from 0.5 to 1.5 mA. If the performance is too high, the microcircuit can be considered faulty.

It is important to measure the output voltage:

• in the absence of a signal, it is equal to the signal voltage;
• when the signal passes, the voltage drops slightly.

If the ESR is too high, the capacitor may malfunction.

The universal board is used to repair many models of split systems, but not all of them. Cheap models have a minimal set of functions, while expensive ones provide full operation of modern air conditioners.