Kaisai E2 fault code

What it means

Zero-crossing signal detection error

The indoor board cannot detect the mains zero-crossing point (no signal, or a bad interval, for ~4 minutes) — usually a supply problem at the indoor unit (most often a missing/poor neutral) rather than the board itself.

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

E2 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.