Is Your Aircon Thermistor Faulty? Here’s How Much It Costs to Fix
Does your aircon keep shutting off on its own, or does the room temperature never match what you set? A faulty aircon thermistor is the most likely cause. The thermistor is the small sensor that tells your unit’s control board how hot or cold the air actually is. Once it fails, the board can no longer regulate the unit properly. This page covers what the part does and how to spot a faulty one, plus what a replacement actually costs in Singapore.
What Is an Aircon Thermistor?
It is a small electrical component fitted inside the fan coil unit and the condenser. Its resistance to current changes with temperature, so as the surrounding air cools, the resistance climbs. The current flowing through it at any moment reflects the temperature at that moment. It is compact, sturdy against shock and highly sensitive to heat. Because of that, the same part turns up in all sorts of everyday appliances, air conditioners included.
An air conditioner cools a room by absorbing heat through the evaporator coil, then expelling it outdoors through the condenser. Thermistors in both the indoor and outdoor units are what let the system track that process accurately. You may also see it called a temperature sensor. Aircon thermistor price depends on the type and brand. Replacement cost also depends on the model and how difficult the part is to access.
Aircon Thermistor vs. Aircon Thermostat: What’s the Difference?
The thermistor is a sensor that measures temperature and converts it into an electrical signal. An aircon thermostat, by contrast, is the control device that uses that signal to regulate the air conditioner’s operation. The two work as a pair: the thermistor feeds temperature data to the thermostat, and the thermostat uses it to keep cooling accurate and consistent.
The thermistor detects the temperature of the ambient, return or supply air, or of a nearby part like the evaporator coil. That reading is then converted into an electrical signal for the control board. It then compares that signal against your set temperature and decides when the compressor should run.
How to Locate and Test the Thermistor
The indoor thermistor usually sits right next to the evaporator coil. The outdoor thermistor is near the condenser instead, attached to the end of the copper tube. A thermistor is a copper sensor head on the end of a wire, so it is easy to spot once you know where to look. The wire itself connects to either the control board or a nearby surface box.
To test one, disconnect the wire connector from the sensor and reconnect a new thermistor that matches your aircon model. Check the resistance reading with a multimeter, then plug the unit back in. Only attempt this if you have the right tools and can identify which wire belongs to which component. A mix-up can damage other parts of the unit.
Two Types of Thermistor: Indoor and Outdoor
AC thermistors measure supply and return air temperature, coil temperature, and water temperature. Exactly which one depends on where they sit. Replacing one means swapping out the exact thermistor that has failed. The part itself is usually inexpensive, but the labour is fiddly. A technician has to dismantle the unit carefully without damaging the parts around it.
Indoor Thermistor
This is the thermistor fitted inside the indoor unit, and it is the one used to measure coil temperature. Keeping evaporator coil temperature well managed matters for optimising your aircon’s energy usage. That, in turn, can help you save on electricity.
Outdoor Thermistor
This one sits inside the outdoor unit, attached to the end of the copper tube. It connects to the main control board out there. If the resistance it measures falls outside the expected range, it signals a fault to the motherboard. An error code then appears, and the unit is likely to shut itself down before any more damage can occur.
How to Tell if Your Aircon Thermistor Is Faulty
A thermistor rarely spoils on its own and can usually last the entire lifespan of an air conditioner. That said, certain aircon brands use thermistors that fail more easily than others. The two most common causes are rust and corrosion, or wires that have become broken, cut or frayed.
Check for an Error Code
This is by far the easiest way to confirm a faulty thermistor. The error can show on the indoor unit, the outdoor unit or the remote control. On a Mitsubishi aircon, a faulty indoor thermistor makes the aircon light blink a set number of times. Remove the fan coil cover to read the pattern, which tells you the thermistor needs replacing. On a Daikin aircon, the same error code shows on the remote control instead.
Measure Resistance With a Multimeter
Sometimes the thermistor fails to report the fault, often because of a bad wire connection. If you suspect that is happening, use a multimeter to check the thermistor’s resistance value. Replace it if the reading falls outside the expected range.
How Much Does It Cost to Fix an Aircon Thermistor?
Price in Singapore depends on the type of thermistor and the brand involved. Reconditioned spare parts are also an option, since thermistors tend to last a long time. An indoor aircon thermistor typically costs between $90 and $160, depending on the brand and whether it is new. The outdoor part usually runs $150 to $250. The exact price depends on brand, condition, and how many thermistors your unit needs replaced.
| Thermistor Type | Estimated Price (from) |
|---|---|
| Indoor Thermistor | $90 |
| Outdoor Thermistor | $150 |
Aircon Thermistor Spare Parts You Can Buy
If you already know your model, here are real Mitsubishi thermistors in stock, each priced at $100.
What Our Customers Say
Real feedback from customers who booked a thermistor replacement or repair with Silverback Aircon, shared on Facebook, Carousell and Qoo10.
Common Questions About Thermistor Repair
There are thermistors in both the fan coil and the condenser unit. Different aircon models use different types for the indoor and outdoor units. A Daikin condenser, for example, typically has gas, air and pipe thermistors in the condenser area alone.
Yes. The PCB can also cause an error code to display as a thermistor failure. It’s worth having a technician confirm which part has actually failed before you order a replacement.
Yes, but rarely, and only when we happen to have excess spare parts for that specific aircon model in stock.
Get Your Aircon Thermistor Fixed Today
Still unsure whether your aircon thermistor has malfunctioned? It’s worth calling a professional aircon repair company to check it out. Silverback Aircon sells a wide range of aircon spare parts and handles the repair too. Call us at 96515152 to check pricing or arrange a replacement.
