Fault route
CT-312 TIG Mode No Gas No HF Diagnostic
A CT-312 TIG-mode route for cases where torch trigger produces neither gas nor high-frequency start.
Quick Answer
If TIG mode has no gas and no HF, start with the torch switch and mode-control path, not the output stage. A missing trigger/mode command can block both gas valve output and HF command.
Diagnostic path
TIG mode switch → torch input → bottom-board support/control path → gas-valve output → HF command.
Evidence table
No gas and no HF: shared TIG support/control issue. Gas works but no HF: use no-HF route. MMA works: shared inverter likely not first suspect. All modes fail: move to inverter/output path.