Daikin Mini-Split Not Heating: Causes and Fixes
Quick Answer
Daikin mini-split not heating: first check that mode is set to HEAT (sun icon on remote) and outdoor temperature is within the unit's range (standard models work to about 20F, FTXM Quaternity to -13F). If the unit is in defrost mode, the indoor fan stops blowing warm air for 5-10 minutes every 30-90 minutes - this is normal. If the outdoor unit is not running at all, check for a stored error code on the indoor unit LED.
When a Daikin mini-split is not heating, first understand that heat pump efficiency drops as outdoor temperature falls. Daikin units are rated to heat down to -13F on some models (FTXM Quaternity series) but standard FTXS models lose significant capacity below 20F. If the outdoor temperature is within the unit's rating, check for defrost mode first - the indoor unit stops blowing warm air for 5-10 minutes while the outdoor unit defrosts its coil. This is normal and happens every 30-90 minutes in cold weather. If the unit is genuinely not heating: check that mode is set to HEAT (sun icon), verify the outdoor unit compressor is running, and clean the outdoor coil of ice or debris.
What Does the NOT-HEATING Code Mean?
Check if the unit is in defrost mode (normal pause every 30-90 minutes in cold weather). Verify HEAT mode is selected and outdoor compressor is running. Clean outdoor coil of ice.
Most Likely Causes
Based on aggregated repair data, here is the probability breakdown for this error code:
Symptoms You May Notice
- Indoor unit blows room-temp or cool air
- Outdoor coil covered in thick ice
- Indoor unit stops and starts every 30-90 min
- Outdoor fan runs but compressor does not
- Steam from outdoor unit during defrost (normal)
Can you reset a Daikin minisplit to clear the NOT-HEATING code?
Breaker off 30 seconds. For iced coils, you can run the unit in COOL mode briefly (5 minutes) to force the outdoor coil to heat and melt ice, then switch back to HEAT.
Tools Required for Diagnosis
Diagnostic Checklist
Follow these steps in order. We start with the easiest external fixes before opening up the machine.
Verify the remote is set to HEAT mode (sun icon) and setpoint is
Verify the remote is set to HEAT mode (sun icon) and setpoint is above room temperature. Wait 10 minutes - if the outdoor unit makes a whooshing sound and steam comes off the coil, it is in a normal defrost cycle and will resume heating shortly.
Check the outdoor coil for ice buildup
Check the outdoor ambient temperature
Replacement Parts
If your diagnostic testing proves the component has failed, you will need a replacement. We recommend OEM parts over aftermarket for water-handling components.
| Part Name | OEM Number | Estimated Price |
|---|---|---|
| Daikin Outdoor Defrost SensorModel-specific · $20–$40 | Model-specific | $20 – $40 |
| Daikin Defrost Control BoardModel-specific · $80–$200 | Model-specific | $80 – $200 |
Repair vs. Replace Calculator
Frequently Asked Questions
Why does my Daikin stop heating every 30-60 minutes?
Can a Daikin heat in very cold weather?
Should I run my Daikin in auto or heat mode during winter?
Related Daikin Minisplit Error Codes
Models Known to Experience NOT-HEATING Errors
This repair applies to most Daikin minisplits with this error code. Common model numbers include:
FTXS09LVJU, FTXS12LVJU, FTXM15QVJU, FTXM18QVJU, FTXM24QVJU
Last verified for technical accuracy on March 15, 2026