Outdoor Air Thermistor Abnormality

Home Appliance Error Codes Daikin Split AC

Can you still use it? With care until repaired

Who can fix it? Needs a technician

Typical repair time 30 minutes – 2 hours

Typical cost SAR 80 to 2,500

What it means

This code appears on Daikin split, ducted and cassette air conditioners and means the thermistor that measures the air around the outdoor unit is reading implausibly because of an open or short circuit. The unit uses this reading to set compressor and fan speed, so depending on the model it stops or runs with limited performance. The same code can mean something else on other brands.

Models covered: Daikin split air conditioners and Daikin ducted/cassette (SkyAir) units, which share the same error code system; the code shows on the wired remote or via the wireless remote check function.

Symptoms3

Code H9 appears and cooling stops or weakens.
Odd changes in outdoor fan speed.
The unit may run in a limited way depending on the model.

Possible causes4

A loose or corroded sensor connector on the outdoor board.
A thermistor damaged by extreme heat, moisture or age.
A sensor wire cut or chewed by rodents or insects.
A faulty sensor input circuit on the outdoor PCB.

How to diagnose4

Switch the unit off at the breaker for a few minutes, then restart.
A technician inspects the sensor, its wire and its board connector after isolating power and discharging the board.
The technician measures the thermistor resistance at the current air temperature and compares it with the Daikin table.
If the sensor is good and the code persists, the board's sensor input is checked.

How to fix5

Reseat and clean the sensor connector.
Repair the damaged wire.
Replace the outdoor air thermistor, which on some models comes as part of a sensor set.
Replace the outdoor PCB if its sensor input is proven faulty.
Run the unit and confirm the code does not return.

Repair cost

0–200

200–600

600–1,500

1,500+

In Saudi riyals; the highlighted part is the expected range for this fault.

Most cases end with a new sensor or a wire repair at low cost; the top of the range only applies if the outdoor board must be replaced.

Prices are rough estimates including the part and the technician’s fee, and vary with brand, model and part source.
Prices last updated: September 2026

Frequently asked questions

Does summer heat cause H9?

High temperatures alone do not trigger it, since the sensor is built to read them, but direct sun and dust speed up wear of the sensor, its wire and connector.

Is this code dangerous?

It does not directly harm the compressor, but the unit cannot tune its operation without the reading, so it stops or cools weakly until the sensor is fixed.

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This guide is for information only and does not replace an inspection by a qualified technician. If the fault involves brakes, steering, engine temperature, electrics or refrigerant, do not attempt the repair yourself.

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