Air conditioners have become important fixtures for homeowners, even more so if you live in an area with a hot climate, high humidity, or air-pollutants. AC problems like breakdowns or failures of your air conditioning unit can happen at times you need cool air the most. Regular maintenance is critical to avoid common problems with your split air conditioner and increase its lifespan.
A split air conditioner, also called a ductless split or mini-split, has two main components — the outdoor unit and the indoor unit. The mini-split outdoor unit houses the compressor, fan, and condenser. This unit transfers the heat from the indoor air space to the outdoors, where it dissipates into the environment. Meanwhile, the indoor unit houses the evaporator, expansion valve, and fan, with copper pipes connecting the flow of refrigerant between the indoor unit and the outdoor unit. Additionally, power input can originate from the mini-split indoor unit and transmit to the outdoor unit.
In the context of non-inverter split air conditioners, the compressor operates on a simple ON/OFF mechanism. It functions at full capacity when activated and remains completely deactivated when not in use. In contrast, inverter-based compressors can regulate compressor speed based on the required load. This allows for efficient operation and energy consumption of the split AC. Once you understand the components of the mini-split system, you can effectively troubleshoot your split air conditioner.
Before delving into troubleshooting electrical issues, it’s important to recognize electrical safety. Manipulating the controls of a split air conditioner requires a sound understanding of electrical principles, as the power supplied to the printed circuit board is live. As a safety precaution, always disconnect and isolate the power supply before troubleshooting common issues. I recommend seeking professional help from an HVAC technician if you lack confidence in your abilities. An HVAC technician will troubleshoot your air conditioner safely and prevent further damage to the HVAC unit.
In this article, I’ll explore the primary components of split air conditioners, discuss common problems encountered with these air conditioning systems, and offer a troubleshooting guide to help with a DIY fix.
Here is an overview of the standard controller of the split air conditioner for a better understanding:
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Main Control Printed Circuit Board
The main control board of a split air conditioner includes an input power supply and a microcomputer controller integrated circuit. It also features temperature sensor inputs and outputs for controlling functions such as the compressor, indoor fan speed, outdoor fan speed, and air flow.
The alternating current (AC) input power supply from the mains has to be converted to direct current (DC) voltage. It can then be used to power the integrated circuits and drivers in the electronics circuit of the split air conditioner.
There are two ways to do this. One is by using a step-down transformer where the AC voltage is stepped down to a voltage such as 25V AC or 12V AC. This voltage is then converted to DC via a diode bridge as a rectifier and electrolytic capacitor to smoothen the rectified voltage.
A 3-pin voltage regulator is used to get a fixed 5V DC or 12V DC power supply. These low voltages are used to power the microcomputer, DC relays, and other integrated circuits in the circuit of the AC unit.
The other method is to use switched mode power supply or SMPS, which makes the dimension of the printed circuit board smaller as the bulky transformer can now be replaced with a smaller transformer.
This design is becoming more common as the quest for smaller space is becoming more critical.
There is usually a surge absorber or a varistor connected across the input of the power supply. This device acts to protect the internal circuit of the HVAC unit in the event of a lightning or power surge.
When the power supply to the mini-split device exceeds its voltage rating, it will clamp the voltage by bypassing it to the input source.
This is one device in the mini split system that can be easily damaged if a power surge or lightning occurred beyond its maximum rating.
A fuse is placed in series with the input power supply to cutoff any overcurrent or short circuit that happens in the circuit of the HVAC unit. This is another protective device used in most electronic circuits. It has to be replaced once it is blown.
Read also: What is a Phase Protector?
Infra-Red Receiver Board
For the handheld remote control of the mini-split to send the settings to the controller of the air conditioner unit, there is an infra-red receiver printed circuit board that receives the signals from the handset. This receiver is usually located in front of the air conditioner’s indoor unit and can be identified by a specially made sticker that allows the infra-red frequency to pass through.
Handheld Remote Control
Also known as a handset, the mini-split handheld remote control is where you control the air conditioner settings — such as airflow — remotely by pointing your handset towards the air conditioning unit. Thermostat, timer, operating mode, energy-saving function, fan motor, and sleep mode are some of the functions that are usually available depending on the manufacturer of the AC unit.
Split Air Conditioner Control Troubleshooting Guide
Here is a split air conditioner control troubleshooting guide to troubleshoot common problems with your split air conditioning unit. To prevent electric shock when troubleshooting, make sure mains power is disconnected before proceeding to check the printed circuit board.
| Problem | Possible Causes | How To Check |
| 1) BURNT | A) LIVE-NEUTRAL SHORTED B) LIGHTNING C) SURGE OF POWER LINES | A) CHECK TRACK OR COMPONENT BURNT B) FUSE, VARISTOR OR TRANSFORMER BURNT C) FUSE, VARISTOR OR TRANSFORMER BURNT |
| 2) NOT WORKING | A) FUSE BLOWN B) VARISTOR BURNT C) TRANSFORMER PAD LIFTED D) TRANSFORMER BURNT | A) USE TEST PEN TO CHK AVAILABILITY OF POWER SUPPLY B) USE TEST PEN TO CHK AVAILABILITY OF POWER SUPPLY C) USE MULTIMETER TO CHECK RESISTANCE ( 2-3 OHM) D) USE MULTIMETER TO CHECK RESISTANCE ( 2-3 OHM) |
| 3) COMP. CANNOT CUT IN AND OUT | A) THERMISTOR OPEN/SHORT B) CRIMPING OF THERMISTOR NOT GOOD C) PAD AT THERMISTOR LIFTED | A) USE MULTIMETER TO CHECK RESISTANCE OF THERMISTOR B) USE MULTIMETER TO CHECK RESISTANCE OF THERMISTOR (VERY HIGH RESISTANCE > 1 MEGA OHM) C) USE MULTIMETER TO CHECK RESISTANCE OF THERMISTOR (VERY HIGH RESISTANCE > 1 MEGA OHM) |
| 4) TRIPPED AFTER FEW HOURS ON | OVERCURRENT | REFER TO FUSE RATING OF DISTRIBUTION |
| 5) NOT SENSITIVE | A) WRONG THERMISTOR B) THERMISTOR PLACE AT WRONG LOCATION | A) USE MULTIMETER TO MEASURE CORRECT THERMISTOR B) CHECK TO ENSURE THERMISTOR AT RETURN AIR |
| 6) SENSOR WIRE LOOSE | A) CRIMPING NOT DONE PROPERLY | A) USE MULTIMETER TO CHECK RESISTANCE OF THERMISTOR (VERY HIGH RESISTANCE > 1 MEGA OHM) |
| 7) PCB NOISY | A) BUZZER SHORTED | A) OFF UNIT AND ON AGAIN, CHECK BUZZER |
| 8) FUSE BURNT | A) OVERCURRENT B) LIVE AND NEUTRAL SHORTED C) OVERVOLTAGE | A) USE TEST PEN TO CHK FOR POWER SUPPLY B) USE TEST PEN TO CHK FOR POWER SUPPLY C) USE TEST PEN TO CHK FOR POWER SUPPLY |
| 9) VARISTOR BURNT | A) OVERVOLTAGE B) LIGHTNING | A) USE MULTIMETER TO CHK VARISTOR B) USE MULTIMETER TO CHK VARISTOR |
For optimal performance of your split air conditioner, especially in regions with hot climates, high humidity, or air pollution, regular maintenance is key. Understanding the components of your split air conditioner, including the main control board, infra-red receiver board, and handheld remote control, will help with effective HVAC troubleshooting.
With this troubleshooting guide, you can confidently troubleshoot common problems with your split air conditioner for uninterrupted comfort. When addressing electrical issues, prioritize safety by disconnecting the power supply. I recommend seeking help from an HVAC professional for complex issues with your HVAC system.
Frequently Asked Questions
What is a common problem with a split air conditioning system?
Many homeowners face the problem of a mini-split air conditioner not cooling properly. This may happen if there is a blocked air filter, a congested condensate drain, frost buildup on the evaporator coils, or malfunctions in the thermostat.
Seek help from an HVAC technician if you cannot isolate the issue.
How do I reset my mini-split system?
To reset your air conditioner, turn off the power. Unplug the mini-split and leave the power to the air conditioning unit off for a minimum of 15 minutes. Plug the unit back in and then turn the power back on.
If your air conditioning unit does not reset, contact a professional HVAC technician.
Why is my air conditioner thermostat not working?
If your thermostat isn’t working, it could be due to various reasons. These include a clogged condensate line, a faulty thermostat, an overloaded circuit, or problems with your power supply.
It may be necessary to contact a HVAC technician to evaluate your mini split system.
