LG Mini Split H66 Error Code

What H66 means

CH66 is a function on LG inverter models that detects abnormal communication or bad piping connections between the indoor and outdoor units. LG's dedicated CH66 page splits the response: if it occurs immediately after a new install or relocation, the installation technician must check the communication-cable wiring for misconnections; if it occurs during normal running, it may be a temporary error from unstable electricity - power off or trip the breaker for about 5 minutes and reset. SplitAtlas describes CH66 the same way and stresses its importance after new installation or relocation.

First checks before service

This page currently documents the safe reset triage. If the code returns, use the linked source manual or a qualified technician for code-specific diagnosis.

1. 1. One-time fault event (power disturbance or transient sensor reading) common DIY

   Check: Power-cycle at the breaker/disconnect (or unplug for CPAP), restore, and run the system while watching for the code.

   Fix: If the code does not return after a full run cycle, the fault was transient — monitor, no repair needed.

2. 2. Fault persists after a clean reset occasional pro only

   Check: If the code returns immediately or every session, note the conditions (startup, heating, after rain).

   Fix: A persisting code points at the component the manual assigns to this code — that repair is technician territory.