Daikin Air Conditioner Error Code U8
On systems with two wired controllers, the main and sub controllers are not communicating as they should — usually a setup or wiring issue from installation.
Applies to: Residential split and multi-split systems
Common causes
- Transmission error between the main and sub remote controllers
- Sub remote controllers connected to each other
- Defective remote controller PCB
What to check, in order
- Switch the unit off at the breaker or isolator, wait five minutes, then switch it back on and run it again.
- Check how the two controllers are set: one must be main and the other sub — the controller's manual explains where that setting lives.
- If the code comes back after the reset, stop restarting the unit and book a Daikin service engineer — the faulty part has to be tested and replaced.
Clear the code and test
- Fix what the checks above found first — a filter cleaned, an obstruction removed, the breaker restored. Clearing the code without fixing the cause only brings it back.
- Restore power at the breaker and switch the unit on with the remote.
- Run the unit in cooling or heating for ten to fifteen minutes and watch whether the code returns; some codes only appear after the compressor has run for a while.
- If the unit runs with no code, the fault is cleared. If the code returns, write down the code and whether the indoor or outdoor unit shows it before calling a technician — it speeds up the diagnosis.
When to call a professional
This code usually points to a faulty part, wiring or the control board on a Daikin air conditioner. Run the checks above to rule out the simple causes, then book a technician — and book one straight away if any of these apply:
- The code comes back after you have run the checks and a test cycle.
- You smell burning, see sparks or scorch marks, or the breaker trips.
- Water is leaking and you cannot stop it.
- The fix needs panels opened beyond what your manual describes, or a part tested with a meter, and you are not set up for that.
When you call, give the brand, the code U8, your model number (on a label on the side of the indoor unit) and the checks you already ran. It shortens the visit.
Repair or replace?
This fault is in professional territory: the fix usually means a major part or board-level work, and the labour adds up. If your machine is already well into its service life, get the repair quote first, then compare it with the price of a current equivalent model before you decide. Paying a large share of a new machine's price to repair an old one is rarely the better deal; replacing a machine over one cheap fault is wasteful too.
Parts that may be involved
Remote controller PCB
Parts are model-specific. Find your model number first — usually on a label on the side of the indoor unit — and match the part to that number before ordering.
Questions people ask about U8
What does U8 mean on a Daikin air conditioner?
U8 means: Main–sub remote controller transmission error. On systems with two wired controllers, the main and sub controllers are not communicating as they should — usually a setup or wiring issue from installation.
Can I fix Daikin U8 myself?
Only the preliminary checks. Code U8 usually means a part, wiring or the control board has failed, which is a technician job. Run the checks to rule out simple causes before you book.
How do I clear Daikin U8?
Fix what the checks above found first — a filter cleaned, an obstruction removed, the breaker restored. Clearing the code without fixing the cause only brings it back. Restore power at the breaker and switch the unit on with the remote. Run the unit in cooling or heating for ten to fifteen minutes and watch whether the code returns; some codes only appear after the compressor has run for a while.
Sources checked
The meaning and checks for this code were checked against the sources above in November 2026. Codes vary by model and region; if your manual lists a different meaning for your exact model, follow the manual.