Daikin Mini-Split Code U7
Soft lockout
Signal transmission error on the outdoor unit PCB. The main microcomputer stopped receiving data from the power module for 9 seconds.
Manual wording: “U7 Signal transmission error on outdoor unit PCB (24/30/36 class only)”
Documented for: FTXS-L and H-Series 24/30/36 class outdoor units
Likely causes, most common first
- Defective outdoor unit PCB
- External factor such as electrical noise
What you can safely check yourself
- Turn the system off at the breaker or disconnect switch, wait a minute, and turn it back on once
When to call a technician
The manual's remedy if U7 returns after a power cycle is to replace the outdoor unit PCB. If it does not return, the manual says the cause was likely external and to keep an eye on it.
A Daikin mini-split throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.
Sources
- Service Manual - Inverter Pair FTXS-L Series / FDXS-L Series (SiUS091133) (Daikin, FTXS09/12/15/18/24/30/36LVJU wall mount, FDXS09/12LVJU ducted, RKS/RXS09-36LVJU outdoor) · checked 2026-08-25
- Service Manual - Inverter Pair Wall Mounted Type H-Series (SiUS04-924_A) (Daikin, FTXS30/36HVJU indoor, RKS30/36HVJU and RXS30/36HVJU outdoor) · checked 2026-08-25