Universal boards for the air conditioner are used when it is difficult to find a part for repairing HVAC equipment. On sale there is a large line of models that differ in device and functionality. Boards made in China are sold in a wide price range.
Description of the cheap model QD-U02B and expensive QD-U11A
QD-U02B
The devices are powered by an external transformer. The relay for controlling the compressor has a nominal value of 30 A, for a four-way valve and fans - 5 A. The relay is connected to the working elements by terminal connectors 0.8 * 6.4 mm. A simple microcontroller is enough to receive control signals from temperature and photo sensors.
The receiving board of the cheap QD-U02B model does not have a case and is equipped with indicator LEDs, a control button and a photomodule. The dimensions of the device allow you to install it in conventional wall models. If you can’t insert the board in place of the previous one, each element of the part can be disconnected and sequential installation is carried out.
The control panel is equipped with a small black screen and a small number of buttons. However, to perform all the functions of the board, it is enough.
QD-U11A
The expensive QD-U11A model has a separate module in the housing. It is equipped with a room temperature indicator. You can manually set the required air temperature. The control element has a timer and operation indicator. A flexible cable connects it to the main board.
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 care must be taken during installation.
How does the malfunction of the air conditioner board
When the LEDs blink on the indoor unit and the inability to turn on the split system, we can assume that there was a failure in the software settings. They are eliminated by reprogramming the control element in the service center by codes.
Air conditioning circuits often burn out during power surges. Inverter units are especially sensitive to changes. In such cases, the board must be repaired or completely replaced.
The main malfunctions of the control element and their causes:
- Manufacturers are equipping solid-state switch control circuits for fan operation. In case of failures in its operation, it is possible to suspect a malfunction of the switches. Before repair, be sure to check the resistance of the element. With a value close to zero, the chip must be unsoldered.
- Failures in the operation of temperature sensors and the compressor also indicate a circuit malfunction.
- If the burnt microcircuit is visible to the naked eye, you will not have to measure the resistance. The control is immediately repaired or replaced.
- In some cases, installers make a mistake in interconnects, which also causes the board to burn out. Often a voltage regulator, transformer and diode bridges burn out.
When the control is completely burned out, its replacement is required.
Should I use universal boards
Universal boards are suitable for installation in most air conditioners, but the scope of their use does not go beyond certain boundaries:
- They can only be installed in “on-off” type air conditioners (non-inverter).
- Such control elements are applicable only for installation in air conditioners with fan motors having additional windings. When controlling a PWM motor, an air conditioner with a universal board will operate at maximum speed. For such cases, quenching resistors are acquired.
When powering the motors of the indoor unit with direct current BLDC, the joint operation of the universal circuit and the air conditioner is not possible. For wall-mounted systems, it is better to choose the QD-U03A model.
Differences of expensive controls from cheap:
- Built-in restart function. After turning off the power and its subsequent resumption, the device will continue to work in the previous mode.
- Equipping an evaporator temperature sensor. This element prevents freezing of the internal heat exchanger.
- The presence of the housing on which the element is mounted.
It is worthwhile to understand the features of installing a universal board in an air conditioner.
Replace item
A manual is supplied with the universal board. It indicates how to connect the item to the air conditioner. The instructions have a detailed diagram. The receiver board, temperature sensor and transformer are connected with standard connectors, so with such an operation the risk of error is minimal.
For connecting the board with a four-way valve, compressor and fan, the element has pin-type connectors. 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 you should be careful 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 wires of the fan motor. One of them is allowed on a common wire, neutral. The rest are connected to the terminals of the relay.
The universal air conditioning control board is designed for operation with motors having additional winding leads. One of the wires is common, while the others come from the remaining windings. Wires with lower resistance are designed to power the fan when operating at maximum speeds.
The board has conclusions signed depending on the fan speed - Hi (high), Low (low) and Med (medium).
The procedure for replacing the control panel of a domestic air conditioner:
- Turn off the power to the appliance.
- Disassemble the housing or remove the block cover.
- Pull the item out of the grooves. To do this, you have to unscrew the screws, disconnect the connectors and wires.
- Replace the part with a new one and assemble the air conditioning module.
All procedures are carried out carefully, because if the board is slightly damaged, the device will not work.
Check installed board
The receiving module of the board includes a chip in which there is a sensor, an automatic gain control system and filters to suppress interference. The output contains the following conclusions:
- nutrition;
- general;
- output.
The connection diagram is simple - through several optional resistors and a power filter capacitor.
The first stage of evaluating the health of an element is to check the connection of parts between themselves and with the main board. The receiving chip is checked for current consumption - from 0.5 to 1.5 mA. With overestimated performance, the chip can be considered malfunctioning.
It is important to measure the output voltage:
- in the absence of a signal, it is equal to the voltage of the signal;
- when the signal passes, the voltage drops slightly.
With increased series resistance (ESR), a capacitor malfunction may occur.
The universal board is used to repair many models of split systems, but not every one of them. Cheap models have a minimum set of functions, while expensive models provide full-fledged operation of modern air conditioners.
