2T/4T timing starts from a valid torch switch.
Fault route
TIG 2T/4T Pre-Flow Post-Flow and HF Routing
A sequence-first diagnostic route for TIG gas, HF and control-panel timing faults.
Quick Answer
TIG 2T/4T, gas pre-flow, HF start, current ramp and post-flow should be checked as one sequence. A fault in one layer can look like a gas, HF, panel or control-board problem.
- Use this page when gas timing, HF timing, 2T/4T latching or post-flow behavior is wrong.
- Do not replace the HF board before confirming that the control board is actually sending an HF command.
- Do not replace the gas valve before checking whether the control board is commanding gas output.
Use this page when
- Torch trigger causes incorrect timing behavior.
- Gas, HF or current does not follow panel settings.
- You need to split panel, control board, gas valve and HF board.
Do not use this page when
- Machine is completely dead.
- Input breaker trips at power-on.
- The only fault is a shorted power device.
TIG sequence diagnostic route
Expected route: trigger → pre-flow → HF start → current ramp → arc transfer → post-flow.
Gas should open before welding current/HF transfer.
HF should be active during arc-start, not stuck on forever.
Start/upslope/base/peak/crater settings shape output.
Gas should remain after current stops.
Timing symptom table
| Symptom | Likely layer | Next direction |
|---|---|---|
| No pre-flow gas | Gas output, solenoid, control timing. | Check gas command and valve supply. |
| HF absent but gas works | HF command or HF board. | Check command output first, then HF board. |
| HF stuck on | HF relay/control output/cutoff. | Inspect HF board and cutoff logic. |
| 2T/4T behavior wrong | Torch input or panel/control-board logic. | Check torch switch and panel mode signal. |
| Post-flow missing | Panel timing or gas-control output. | Check post-flow setting and gas output path. |
Related records
Use board references based on the failing layer.