Fault
MIG wire feed not working
Mechanical and control-board diagnosis for MIG wire-feed motor, trigger and 2T/4T logic.
Separate mechanical and electrical causes
MIG wire-feed faults often look like a control-board problem, but many are mechanical: tight spool tension, worn drive rolls, a blocked liner or a damaged contact tip. A proper page must separate these from board-level problems such as trigger input, 2T/4T logic, motor driver or brake circuit failure.
Wire-feed diagnostic flow
Torch trigger pressed
↓
Trigger signal reaches board
↓
2T/4T logic changes state
↓
Gas valve / contactor enabled
↓
Wire-speed command read
↓
Motor driver output appears
↓
Motor turns
↓
Wire feeds smoothly
Board-level checks
| Check | Normal / Expected | Abnormal Meaning |
|---|---|---|
| Trigger input | Changes when trigger pressed | Torch switch or harness issue |
| Wire-speed command | Variable voltage or control signal | Potentiometer or reference issue |
| Motor output | Variable DC/PWM | Driver transistor/MOSFET or relay fault |
| Brake path | Released during feed | Brake shorting motor output |
| Gas valve output | Enabled with trigger | Logic or supply fault |
Common causes
- Torch trigger switch or cable open.
- Wire-feed motor brushes or winding failure.
- TL494/CD4013/LM324 style control logic fault.
- Motor driver transistor or MOSFET short/open.
- Brake circuit remains active.
- Mechanical drag in liner, spool or drive roller.