C-305: Rotation direction fault

Q: How do I check a C-305 fault?

1. Do not restart repeatedly 2. Have a qualified electrician verify phase sequence 3. Bump-test only per OEM procedure Safety: Isolate electrically and vent all stored air pressure before opening any part.

Probable causes

Phase sequence reversed after electrical work
Wiring error

Step-by-step checks

Do not restart repeatedly
Have a qualified electrician verify phase sequence
Bump-test only per OEM procedure

Safety: Isolate electrically and vent all stored air pressure before opening any part.

Sample code — verify with the OEM manual for your exact model.

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Frequently asked questions

What does C-305 mean on a Screw Air Compressor?

C-305 usually indicates: Rotation direction fault. Confirm the meaning in the manufacturer's manual for your model.

What causes C-305?

Phase sequence reversed after electrical work; Wiring error.

How do I check a C-305 fault?

Work through the numbered checks above in order, recording readings as you go. Isolate electrically and vent all stored air pressure before opening any part.

Other Screw Air Compressor codes

Disclaimer: Fault code information is guidance only. Codes and meanings vary between manufacturers and models — always follow the manufacturer's manual and your site's safety procedures, and use qualified personnel for electrical, pressure, refrigerant and combustion work.