Fault route
CT-312 Plasma No Arc but Air Works Diagnostic
A CT-312 plasma-mode route for air or gas present but no arc transfer.
Quick Answer
Air or gas flow does not prove the arc-start or cutting-current path is working. If MMA works, prioritize plasma support, HF/pilot start, torch and work-return evidence before blaming the shared inverter.
Diagnostic path
Air/gas support → plasma mode switch → HF/pilot start → main output path → torch/work return.
Evidence table
Air works with no HF: HF command or HF board. HF present with no transfer: torch consumables, work clamp or main output. MMA also dead: shared inverter/output layer.