Repair Case
MIG Wire Feeder Does Not Run
Use this case page when a MIG/NBC welder powers on but the wire-feed motor does not move after the torch trigger is pressed.
Symptom pattern
The machine may power up normally, the fan may run, and the welding output section may be healthy, but the feeder motor does not rotate. In some machines the gas valve also fails to open; in others the gas valve clicks but the motor remains dead. That difference helps separate trigger-logic faults from motor-drive faults.
First checks before board repair
| Check | Expected result | If abnormal |
|---|---|---|
| Wire spool and feed roller | Motor can turn without mechanical lock | Remove mechanical load before judging the board |
| Torch trigger switch | Clear open/close change at trigger connector | Broken torch cable or trigger switch fault |
| Motor connector | Motor receives DC when trigger is active | No voltage means board/relay/driver path fault |
| Motor direct test | Motor runs from a suitable external DC supply | Dead motor, worn brushes or seized gearbox |
| 24V or control rail | Stable under trigger load | Auxiliary supply drops or feeder board supply missing |
Board-level diagnostic path
Press torch trigger
↓
Confirm trigger signal reaches feeder board
↓
Check 2T/4T latch or logic section
↓
Check speed-control voltage from potentiometer
↓
Check motor driver transistor / MOSFET / relay
↓
Verify motor voltage under load
Likely failed sections
- Open torch-trigger line or bad connector.
- Missing 24V feeder-board supply.
- Failed relay contact feeding the motor.
- Shorted or open motor driver transistor/MOSFET.
- Bad speed potentiometer or broken reference voltage.
- Logic IC or latch fault in 2T/4T control boards.