F1 Module Protection Error

What it means

The power module directly drives the compressor. When it detects overcurrent, overvoltage, or overheat, it stops the compressor and sends a shutdown request to the module panel. The resulting error is called module protection error. L-codes (L0–LC) are subdivided failures of F1 — see those entries for specific subcategory names and primary parts.

Inspection path

Diagnostic procedure

1. Check if the compressor wire order is correct. If wired in reverse, try swapping the U-V phase wires to see if the error clears.
2. Verify supply voltage stability. Measure system pressure — high pressure can cause compressor rotation problems.
3. Confirm the module panel is firmly mounted to the radiator for adequate cooling. Check if indoor or outdoor heat exchangers are dirty, which causes poor heat transfer and elevated system pressure.
4. If the error appears immediately on startup, a physical component failure is likely (unrelated to voltage or pressure). Inspect for strike-arc damage near the module panel. Use a multimeter to confirm equal resistance between any two compressor wires — should be ohm-level and equal across all pairs. Use a megameter to verify insulation resistance of each compressor wire to earth (should be MΩ level). Check that the reactor wire is firmly connected and the reactor is not damaged.
5. Test that the 15V and 5V (or 3.3V) power supplies on the module panel are stable. Rule out power supply issues originating from the main external control panel.
6. Using the diode function on the multimeter, test the power module: measure P against U, V, and W — one direction should show infinite resistance, the other a fixed on-state voltage (typically ~0.5V). Repeat for N against U, V, and W. A short circuit in any measurement indicates a damaged power module.
7. Replace the module panel with a known-good unit. If the unit runs normally after replacement, the original module panel is damaged.
8. After ruling out module, wiring, system, and power supply issues, listen to the compressor. If only electromagnetic sound is present without the compressor starting, or if the compressor runs irregularly then shuts down and indicates error, the compressor may be blocked or damaged.

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