Toshiba air conditioning service
Toshiba 18 and 19 Error Codes
What the 18 and 19 codes mean on your Toshiba, what you can check and when to book a repair.
Seeing a Toshiba 18 error code usually means the system has lost a reliable reading from one of its outdoor temperature sensors. Code 19 is a close relative that points to a different outdoor sensor. Both are protective codes, so the system stops or limits itself rather than run blind.
This page explains what each code generally means, how the sensors work and what you can check without opening anything. We also cover what a technician tests and how these codes relate to the codes shown on wired controllers. Meanings can vary by series, so always confirm against the manual or service label for your exact model.
What does a Toshiba 18 error code mean?
On many Toshiba wall split systems in the RAS series, and on some older RAV units, code 18 points to the outdoor coil sensor. Toshiba calls this sensor TE. The code generally means the controller has detected an open circuit or a short circuit on that sensor.
Sensor faults are not the only codes tied to temperature readings. For example, code 09 appears when the unit runs but the room temperature does not change.
In plain terms, the outdoor board expects a sensible temperature reading from the coil. When the reading looks impossible, such as no signal or a dead short, the board flags it. Then the system stops normal operation to protect itself.
What the TE sensor does
The TE sensor is a small thermistor clipped or strapped to the pipework of the outdoor coil. It tells the outdoor board how hot or cold the coil is running. Because that reading guides several decisions, the system cannot run properly without it.
For example, in heat mode the outdoor coil runs cold and can frost over. The board uses coil temperature as part of its decision on when to defrost. In cool mode, the same reading helps the system manage the outdoor side safely.
Why an open or short circuit matters
A thermistor changes its electrical resistance as temperature changes. The board reads that resistance and converts it into a temperature. So if a wire breaks, the board sees an open circuit, and if insulation fails, it may see a short.
Either way, the reading falls outside a believable range. Rather than guess, the controller stores code 18 and signals a fault.
What does Toshiba error code 19 mean?
Code 19 generally points to the outdoor TL sensor or the discharge TD sensor, again with an open or short circuit. Which sensor applies depends on the model and series. That is one reason it is important to check your manual or the service label.
The TL and TD sensors sit on different parts of the outdoor refrigerant circuit. The TD sensor is associated with the compressor discharge, where hot gas leaves the compressor. Meanwhile, the TL sensor reads another point on the outdoor pipework.
Why the discharge reading is important
The discharge line carries the hottest refrigerant in the system. As a result, its temperature gives the board an early warning if the compressor starts running too hot. Without a trustworthy reading, the board cannot protect the compressor properly.
That is why technicians take a sensor fault here seriously. It is not the same as the compressor overheating, but it removes one of the safeguards.
How 18 and 19 differ from other outdoor codes
These two codes relate to sensor circuits, not to a confirmed mechanical failure. For instance, code 1E generally means a high discharge temperature, while 1d points to a compressor fault. Code 18 or 19 instead says the board cannot trust a sensor.
In practice, a technician still checks the wider system. A sensor fault sometimes appears alongside other problems, so the diagnosis does not stop at the thermistor.
How does a Toshiba aircon show these codes?
Toshiba wall splits usually tell you about a fault by flashing the lights on the indoor unit. Depending on the model, these may include the operation light, the timer light and sometimes a third light. Fast flashing of the operation and timer lights together generally indicates a stored fault.
Indoor sensors have their own codes too. The room temperature sensor shows as code 0C, while the indoor coil sensor shows as code 0d.
Flashing lights versus normal behaviour
Not every blinking light is a fault. A slow, steady flash of the operation light after power returns is normal on many RAS units. In that case, the system is simply waiting, and it is not reporting an error.
People often search for terms such as aircon flashing green light or toshiba air conditioner blinking light when they spot this. However, colours and exact patterns vary between models. So it helps to note what you see rather than rely on colour alone.
Reading the two character check code
On many wall splits, you can read the stored code with the wireless remote. Point the remote at the indoor unit and use the CHECK function. The remote then steps through codes until the unit beeps on the stored one.
Exact button steps vary by remote model, so follow the manual for yours. If you cannot find the manual, a technician can read the code on site.
Codes on wired controllers
Ducted, ceiling cassette, under ceiling and VRF units usually show a letter and two digit code on the wired controller instead. On these systems, outdoor sensor faults generally appear in the F series. For example, F06 relates to the outdoor TE sensor, F07 to the outdoor TL sensor and F04 to the discharge TD sensor.
Our guide to F series error codes explains those in more detail. On many wired controllers, holding the CHECK button also recalls the fault history.
What usually causes code 18 or code 19?
Because these are sensor circuit codes, the likely causes are fairly predictable. Even so, only proper testing confirms which one applies. The list below covers the usual suspects.
- A thermistor that has failed internally with age or heat
- Sensor leads damaged by vibration, sharp edges or pests
- Loose or corroded plugs where the sensor connects to the board
- Moisture or corrosion around the connection, especially near the coast
- A fault on the outdoor board itself, in the sensor input circuit
In many cases, the sensor or its connection is the problem rather than the board. That said, a technician tests both before replacing anything.
Weather and location factors
Outdoor units sit in sun, rain, wind and salty air. Over time, these conditions wear on wiring and connectors. Therefore, units near the sea or in exposed spots may show sensor faults more often than sheltered ones.
Rodents and insects can also cause trouble. A chewed lead or a nest near the board can create an intermittent open or short circuit.
What can you safely check yourself?
Some owner checks are worth doing before you book. They will not repair a failed sensor, but they can clear a temporary glitch and give the technician useful information. Never open covers, touch wiring or handle refrigerant during any of these steps.
- Note the code and the light pattern exactly as you see them. If you can, take a short video of the flashing lights.
- Turn the system off at the isolator switch near the outdoor unit or at the switchboard.
- Wait a few minutes, then restore power and see whether the code clears.
- Check that the outdoor unit actually has power and that the isolator is on.
- Make sure nothing blocks the outdoor unit, such as plants, covers or stored items.
- Clean the indoor filters and check that the drain outlet is clear.
If the code returns quickly after a reset, the sensor circuit probably has a real fault. In that case, leave it switched off and arrange a check.
What not to do
Please do not remove the outdoor cover or try to test sensors with a meter. The outdoor unit contains mains voltage and, on inverter models, components that can hold charge after power is off. Also, avoid unplugging and replugging board connectors, because this can damage pins or introduce new faults.
Refrigerant work is a separate matter entirely. In Australia, it requires a technician holding an ARC refrigerant handling licence.
If the outdoor unit has stopped
Sometimes these codes appear alongside an outdoor unit that has gone completely quiet. If that is your situation, our guide to an outdoor unit not running covers power and other causes. It helps you separate a sensor fault from a supply or protection issue.
How does a technician fix a Toshiba 18 error code?
A technician starts by confirming the code and checking the fault history if the controller stores one. Then they isolate power safely and open the outdoor unit. The aim is to find out whether the sensor, the wiring or the board is at fault.
Typical diagnostic steps
The process usually follows a logical order. First, the technician inspects the sensor, its lead and its plug for visible damage or corrosion. Next, they measure the sensor resistance and compare it with the expected value for the temperature.
If the sensor tests out of range, replacement is the usual fix. If it tests fine, the technician checks the wiring and then the board input. That way, they avoid swapping parts that are not faulty.
Replacing a sensor
Replacing a thermistor is generally a straightforward job once the right part is on hand. The technician fits the new sensor in the correct location on the pipe and secures it properly. Correct placement matters, because a loose or misplaced sensor can give poor readings.
After fitting, they restore power and run the system in both modes where possible. Then they confirm that the code has cleared and that temperatures read sensibly.
When the board is the problem
Occasionally, the sensor and wiring both test fine but the code remains. In that case, the outdoor board may have a fault in its sensor input. A board replacement is a bigger job, and the cost depends on the model and part availability.
A good technician explains this before going ahead. You can read more about how we approach these jobs in our Toshiba air conditioner repair guide.
Why do meanings vary between Toshiba models?
Toshiba has produced many series and generations over the years. Wall splits, ducted units and VRF systems use different controllers and code formats. As a result, the same number can carry slightly different meanings on different equipment.
The meanings on this page come from published Toshiba code references and apply to many RAS wall splits and older RAV units. However, they are not a fixed rule for every model. Therefore, always check your manual or the service label, which is often inside the outdoor unit cover or on the indoor unit.
Finding the right information
Start with your model number from the rating label. Then look up the manual for that model if you have it. If not, give the model number and the code to the technician when you call.
Our full list of Toshiba air conditioner error codes is a useful starting point for other codes. It also explains how the code families relate to each other.
Frequently asked questions
Can I keep using my Toshiba with an 18 error code?
It is best not to. The system stops or limits itself because it cannot trust a key reading. Leave it off and arrange a check so a technician can test the sensor circuit.
Will turning the power off and on clear the code?
A reset sometimes clears a temporary glitch. However, if the sensor or its wiring has a real fault, the code usually returns. In that case, a technician needs to test the circuit.
Is code 19 more serious than code 18?
Both are sensor circuit faults, so neither confirms a mechanical failure. Code 19 involves the TL or discharge sensor, which helps protect the compressor. Treat both seriously and avoid running the system until it is checked.
Does a Toshiba error code always mean a part has failed?
Not always. Loose plugs, corrosion or a damaged lead can trigger the same code. Proper testing shows whether the sensor, the wiring or the board needs attention.
Why is my aircon light flashing but no code appears?
Some flashing is normal, such as a slow flash after power returns. If the lights flash fast together, try reading the code with the remote CHECK function. If you cannot read it, note the pattern and pass it on to the technician.
Do ducted Toshiba systems show code 18?
Ducted and other wired controller systems usually show letter and number codes instead. Outdoor sensor faults on these systems generally appear in the F series. Check your controller manual for the exact code.
Can bad weather cause these codes?
Weather does not usually cause the fault directly. Still, rain, heat and salty air can wear wiring and connectors over time. That gradual wear can lead to an open or short circuit.
How long does a sensor repair take?
It depends on the model, the access and whether the part is in stock. Testing and replacing a sensor is often a single visit. A board fault may take longer if the part needs ordering.
Next steps for an outdoor sensor fault
Codes 18 and 19 both say the outdoor board cannot trust a sensor reading. Usually, the cause is a failed thermistor, a damaged lead or a poor connection. Start with the safe checks, note the code and light pattern, and confirm the meaning against your manual.
If the code keeps returning, you can contact us to arrange a local technician. They will test the sensor circuit properly and explain what needs fixing before any work begins.
Talk to us about your Toshiba system
Tell us the model, the fault and your suburb, and we will book a local technician.
Book a technicianCall 1300 495 033Independent service provider. Not affiliated with Toshiba.