Troubleshooting guide › Process troubleshooting › MIG / MAG welding problems
Nine out of ten MIG problems are in the wire path or the gas path, not in the power source. This page works through them in the order a technician would check them: the feed, the torch, the gas, the earth, then the settings, and finally the machine protections. Each symptom has its likely causes first.
Reviewed by the Cruxweld technical team, October 2026. Settings are starting points to confirm on a test piece; acceptance is decided by the code or drawing the job is built to. Checks marked “call” are for our technical team.
The wire should come out of the torch at a steady rate with the trigger pressed and the drive rolls turning. If it stutters, slips, or stops, work down this list.
Too little pressure and the roll slips; too much flattens the wire so it jams in the liner.
Copper dust and drawing lubricant build up inside the liner; a kinked torch cable binds the wire.
An oval, enlarged tip bore gives poor contact, so the arc wanders and the wire can weld itself to the tip.
A V-groove for solid wire; a knurled V for flux-cored; a U-groove for aluminium. A worn groove slips.
Too tight and the motor stalls at the start; too loose and the spool overruns and tangles.
Wire scrapes the guide tube, picks up shavings and jams.
Rust and dust act like sandpaper in the liner.
Feed motor does not run at all, or runs at one speed regardless of the setting.
The drive rolls keep pushing but the wire cannot get through the torch, so it bunches into a nest behind the rolls. The blockage is always downstream of the rolls.
To clear it: release the pressure arm, cut the wire at the spool side and the torch side, pull the nest out, snip a clean end on the wire, and re-feed. Never pull the wire back through the liner.
The arc stays on after the feed stops and burns the wire back into the tip.
The arc melts wire faster than it arrives and climbs back to the tip during the weld.
Every momentary feed stall is a burnback.
Nozzle and tip held almost on the plate.
Loose tip overheats and grabs the wire.
The most common cause. A clamp on paint, scale or a rusty bench adds resistance and the arc flickers.
A sputtering, popping arc with big spatter means too little voltage; a long, hissing arc with the wire burning back means too much.
Current transfer to the wire becomes intermittent.
See wire feed above.
The arc follows the supply. One missing phase on a three-phase machine gives a weak, unstable arc and overheats the machine.
A cable with broken strands inside the insulation heats up and drops voltage under load.
Welding solid wire with no gas gives a violent, spattering arc and a black porous bead.
See the porosity page for the full list once the gas path is proven.
| Symptom | Likely cause | What to do |
|---|---|---|
| Power lamp off, fan off, no display | No supply, phase loss, circuit breaker open, input fuse | Check the isolator and all three phases; reset the breaker once; if it trips again, call service |
| Protection or over-temperature lamp on, no output | Duty cycle exceeded, fan blocked, ambient over 40 degrees C, or mains over-voltage | Leave the machine on so the fan cools it; it resets itself. Clear the air inlets. If it trips often, the machine is too small for the job |
| Fan runs, no arc, no wire | Trigger or control cable fault, feeder plug loose | Check the control plug and the torch trigger continuity |
| Wire feeds but no arc | Earth not connected, contact tip not conducting, output cable loose | Check earth clamp and the output socket lugs |
| Arc weak, cannot reach the set current | Supply voltage low, cable too thin or too long, one phase missing | Measure the supply under load; use the cable size the machine specifies |
| Breaker trips every time at switch-on | Internal component fault | Do not keep resetting; call service |
| Current varies by itself | Mains swinging, interference from a nearby large load | Move to a separate supply line; an inverter with voltage compensation holds the arc better |
| 3 mm plate, fillet | 130-160 A, 19-21 V, dip transfer, 12-15 L/min |
| 6 mm plate, fillet | 200-250 A, 24-27 V, 15-18 L/min |
| 10 mm plate, fillet | 260-300 A, 28-31 V, 18-20 L/min |
| 12 mm plate, multi-pass | 280-330 A, 30-34 V, 18-22 L/min |
| Contact tip to work | 10-15 mm below 200 A; 15-20 mm at 200-350 A |
| 0.8 mm wire, 1-2 mm sheet | 50-90 A, 15-18 V |
| 1.6 mm wire, heavy plate | 350-450 A, 32-38 V, water-cooled torch |
Starting points for CO2 or Ar-CO2. Ar-CO2 runs 1-2 V lower for the same bead. Confirm on a test piece.
Thermal protection. The machine has reached its duty cycle at that current. Either the job needs a larger machine, or the air inlets are blocked with dust, or the ambient is very high. Check the fan and filters first.
A separate feeder lets the operator move 10-15 m from the power source with a short, light torch cable, so the wire path is short and feeding is reliable. For a fixed bench, a built-in feeder is simpler.
Yes. Fit knurled drive rolls, check the polarity the wire asks for, and use the gas it needs (gas-shielded FCAW) or no gas (self-shielded). Voltage runs 1-3 V higher than solid wire.
The wire is live and touching the feeder body, usually because the inlet guide insulation is worn or the torch connector is loose. Isolate and fix before use.
Lamps, fault codes and the checks an operator can do outside the cabinet, for the machines this page applies to.
Most of these faults are in consumables that any machine uses: liner, contact tip, feed rolls, nozzle. The machine matters for arc stability (an inverter holds the set voltage through mains swings), for duty cycle (a machine that trips on thermal protection every 20 minutes is too small for the job) and for the feeder (a 4-roll feeder with a separate motor control feeds 1.6 mm and flux-cored wire without slipping).
Send a photo of the weld or cut, your machine model, consumable and plate thickness. Our technical team replies on WhatsApp with the likely causes and the next checks to make.
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