Kaisai E1 fault code

What it means

Indoor ↔ outdoor unit communication error

The indoor unit received no feedback from the outdoor unit (110 s, four times running). Work the interconnect and both boards.

Safety: Safe isolation before opening terminal covers — mains present on the interconnect.

UK models this code applies to

From the Kaisai service literature we hold (KAISAI FLY Inverter Series B (KWX) R32 service manual, §4 Quick Maintenance by Error Code (p.65, render-verified) + §5 Troubleshooting by Error Code) — not a scraped list.

Now the harder half: proving what caused it

E1 names a symptom, not a root cause. In the app, the same code opens a guided investigation: what to measure first, the expected values for your exact model, and an honest verdict — including “nothing in this machine is broken” when that's what the readings say.