MIG Welding Trouble Shooting: The Ultimate Guide Ever!

If you’re yet to figure out the least demanding and straightforward part of metal fabrication, MIG welding makes a good example. But, it may get complicated all too quickly when you cannot overcome the many problems that occur in the process. Can’t you do better than turning to a repair professional every time things happen? We know you can, and here’s a comprehensive MIG Welding Troubleshooting guide to show you how.

What Will You Learn from This Article?

# 20 causes of Porosity problems

# 15 common Wire Feed problems

# 3 Welding Bead issues

# 3 Fusion and Penetration Problems

# 6 MIG Weld Defects

# 5 MIG Welding Machine issues

Most of the problems discussed in this article are common with some occurring once in a while. Understanding the causes and following the suggested procedures will help you go a long way in this line of work

MIG Welding Porosity Problems: 20 Causes and Solutions

Porosity isn’t much of an outcome a MIG welding professional would want to have, but it’s too common for them to ignore and stop trying to prevent. So, knowing what it is, what causes them to show up frequently, and how to prevent them is important.

What Is Porosity in MIG Welding?

Technically a trapped gas, porosity is a kind of contamination of weld metal. When the torch is applied to treat metal the action results in the release of gases. That get absorbed directly into the molten metal and subsequently released while solidification occurs.

The shielding gas may not make it to the weld pool causing the atmospheric air to affect the weld bead adversely. The problem starts surfacing in the form of rounded holes; otherwise termed as spherical porosity. Some holes that become elongated are known as piping or wormholes.

What Causes Porosity in MIG Welding?

Three major factors are responsible for this. The material conditions, gas flow, and other welding consumables are exactly the things you want to inspect. Look at the 22 causes that create porosity in MIG welding and learn how to prevent porosity in MIG welding.

Due to certain welding standards, porosity can be a serious defect. In other cases, the problem can be acceptable to some extent. Since its prevention rate is as high as 90%, you surely can give it a try.

Cause                      Solution
The cylinder with no gas in itEnsure that the cylinder has gas to its full capacity
Air or drafts from floor/overhead fans, open doors, and nearby machineryPrevent the sources of air or similar drafts
Moisture from water, condensation due to welding (at/below 50 degrees F), morning dewEvaporate the moisture by preheating the metal to 200 to 220 degrees F
Restricted or plugged GMAW (Gas Metal Arc Welding) gun nozzlesCheck the nozzle opening every time before doing a weld to stop weld splatter from getting mixed with the weld
Diminishing shielding gas due to the weld nozzle and the weld puddle being distancedKeep the required distance
Inaccurate angle for holding the GMAW gunMaintain an angle that is perpendicular to the metal joint (5 to 15 degrees)
Large volume of gas released by surface contaminants like glue, grease, oil, paint, and sweat being exposed to arc weldingKeep the surface clean by using chemical solvents or grinder before any welding operation
Moisture welcomed by decomposition gases and oxidation resulting from welding rust or mill scaleUse oxidation remover
Gas and zinc dust generated from plating compounds using zincLearn the rules of welding galvanized material perfectly
Presence of moisture begotten by FCAW and SMAW electrodes and SAW fluxBeware of the rules of using ovens and dryers for storing these materials or abide by the manufacturer’s directions
Too high gas flowMaintain the GMAW nozzle’s flow at 50-60 cubic feet per hour and the GTAW torch’s at 20-30 cubic feet per hour
A contaminated/burnt/cut/smashed/pinched gas hoseRepair or replace if smashed or pinched and clean if contaminated
Wrong use of gels, sprays, or anti-spatter compoundsUse the compounds properly or leave them completely
Contaminated weld filler materials with items like glue, grease, oil, paint or tapeUse wire wipes to cleaning solid and/or flux-cored wire and use steel wool for GTAW fillers
GMAW gun liners contaminated with surface materialsKeep the liners clean and tidy  
Gas metal arc welding on an outside corner joint’s edgeUse the nozzle to cover the joint perfectly
Open weld joint at the rootClose the joint before it sucks in the outside air
Contaminated welding gasBuy gas with the correct dew point
Presence of air due to broken O-ring seals on the gun whipReplace the seals
A defective/faulty gas solenoidReplace the solenoid

At this point of our MIG Welding troubleshooting guide, you’ll be gathering ideas about another common area of problems, the wire feed system.

MIG Welder Wire Feed Problems: 15 Examples and Solutions

The MIG welder wire feed can be a source of many MIG welding problems. Most of these issues are interconnected, and they call for specific skills. So, the chances are that you can fix multiple problems by taking one or two steps.

#1 Birdnests

Two signs help you identify the problem. The electrode wire may wrap around the drive roll. Also, you may see the tangled wire. Both can lead to halted wire feeding.

Excessive pressure on the feed rollAdjust the pressure
Misaligned wire guides and/or drive rollsAlign the guides or rolls properly
Restriction in cable and/or torchEliminate restrictions

#2 Tangled Wire (Off the Reel)

The wire reel suffers some kind of inertia that forces it to coast and keeps doing this as you release the gun trigger. Eventually, the wire becomes loose and come off its reel only to become tangled.


The majority of wire feeding systems feature an adjustable brake. Set the brake tension appropriately to prevent the wire reel from coasting.

#3 Burnback

As the arc gets over the wire, it may cause a burn back issue by fusing the wire quickly to the contact tip.

Slow wire feed speedIncrease the speed
The gun and the base metal being positioned too close to each otherKeep the gun and metal moderately distanced
Too high welding currentAdjust the current
Use of Ar-CO2 or Ar-O2Use CO2
Electrode wire kinkedReplace the spool or cut out the kink

#4 Motor Running but No Wire Feeding

Sometimes, you might see the wire feed motor is in an operational mode but without signs of wire feeding. This issue is mechanically associated with birdnesting. So, you may check on the contact tip, the liner, and the torch for any restrictions or impropriety.

Drive roll pressure not sufficientAdjust the pressure
Improper wire feed rollsMatch the feed roll to the size/type of the wire
Wire spool brake suffering excessive pressureReduce the pressure on the brake

#5 Wire Feeding Stopped while welding

You’ve started welding with ongoing wire feeding. All on a sudden, it stopped, and there’re obvious reasons.

Blown fuses in the primary line, protective, and control circuitReplace blown fuses
Open welding machine contactorTake care of the open circuit volts
Defective control relayReplace the relay
Misaligned wire drive rollsRealign the rolls
Excessive frictions in the wire feeder’s spindleLoosen the nuts and readjust their pressure
Excess drive motor loadsClear the restriction if there’s any in the drive assembly
Burnt-out drive motorCheck for damages and replace the motor
Torch liner or casing is broken/damaged or having excessive frictionsCheck for clogging or damages. Replace the parts if necessary
Defective torch trigger leads or switchCheck the connections and replace the switch if necessary
Cables/Liner having excessive/sharp bendsStraighten the cables and replace the lines

#6Wire Feeds without gas flow

That the wire feeding continues is not always the sign of proper functioning. If the gas doesn’t flow well or at all, it’s a trouble.

Gas valve solenoid failureReplace the solenoid
Broken or loose wires attached to the gas valve solenoidIncrease the tension or replace it if it’s broken
Empty gas cylinderReplace and purge the lines prior to welding
Closed gas cylinder valveOpen the valve
Flow Meter/Regulator not properly adjustedAdjust the regulator/meter
Restriction in the nozzle, or gas line, or torchClear the restriction
Clogged or pinched coolant lineRemove any obstruction in the line
Coolant level very low in the pump reservoirAdd coolant as required
Malfunctioning water pumpCheck for issues and replace if not fixed

#7 Wire Feeding-without Arc Strikes

As the wire feeding starts, the arc should be struck. When you see otherwise, it should be taken care of.

Blown primary line fuseReplace the fuse
Contactor plug loosened in the socketTighten the plug in the receptacle
Broken contactor control leadsReplace the leads
Broken/Wrongly positioned remote/standard switchCorrect the positioning or replace it
Defective primary contactor points or coilReplace the items
Cable connection loosenedTighten the cable connection
Poor connection in the work piecesClean the work pieces and tighten them
Contactor plug wrongly or not seated at allTighten the plug

#8 Slow Wire Feed Start

Does the wire feed start slower than expected? It isn’t a big deal. Maybe, it’s set to be that way in the run-in control.


You can change the speed, or wait for the arc to be established because it’s when the speed will increase.

#9 Irregular Wire Feed

It’s not uncommon for the wire feed to act irregular. Let’s check out the probable causes and the best solutions.

Fluctuations in the power circuitCheck up on the line voltage
Wrong polarityReverse the leads
Drive roll pressure not adequateIncrease the pressure
Worn or dirty conduit linerReplace or clean the liner
Wrong length of the conduitRemove the extra length or get a push-pull system

#10 Wire not passing through the torch

If the wire doesn’t pass through the torch, you cannot really expect any sort of operation to go on. In addition, it may pose a ‘bird nesting’ situation. The contact tip may not be sized correctly. The gun liner can also be the culprit.


Choose the size of the contact tip and the gun liner keeping the wire in mind.

#11 Inconsistent Arc Length

The length of the arc if not consistent can be the reason why you may not expect it to work appropriately. Try the following tips.

  • Adjust the Spool hub tension
  • Check the condition of the drive roll groove and adjust its tension
  • Find the correct size of the contact tip

#12 MIG Welder Liner Problems

The gun liner is critical to the feed delivery system. Any impropriety in its size or clogging inside it may lead to faulty wire delivery problem. Just two tips are effective. Find the accurate size for the specific wire being used and keep it clean allowing no dust or debris to form inside.

#13 Faulty Wire Delivery: Problematic Contact Tip

The contact tip picks up unwanted particles from extra spatter. It may even get clogged when touched on the weld puddle. The size of the tip also matters. In any of these case, you’re going to experience troubles in the wire delivery system. So, keep checking for wears and clogging and clean it whenever possible. Choose the size perfectly too.

#14 Wire Feeding Problem: Worn Out Gun

There’re copper strands located inside the gun, which are prone to breaks/wears over time. While replacing one, choose a size that is large enough to suit your needs.

#15Drive Roll Worn Out or Slipping on Wire

Too tight to loose, the drive roll can be the cause of zero wire feeding, crushed wire, and other MIG wire feed problems. It’ll eventually place excessive or poor pressure on the drive shaft only to result in a worn roll and damaged motor.

No set rules apply to the amount of pressure required. Not too loose or tight is the way to go. Adjust the rolls side by side so that they stay in the same line as the inlet guide and all the way to the gun. Sometimes, a replacement is the only solution.

MIG Welding Bead Problems: 3 Causes and Solutions

A weld bead is the filler material deposited by a welding pass and looks like a round deposit. Anything like a concave or convex shape indicates that the bead profile isn’t correct or good enough.

Such a welding discrepancy can be a result of insufficient heat input, applications of improper technique, or the use of work cable.

Improper settings generate insufficient heat which barely penetrates into the metal being welded


Figure out the right amperage considering the workplace conditions using the manufacturer’s directions. High amperage settings for inaccurate voltage settings may lead to different issues like spatters and undercuts. You should hear a steady noise from a running arc if proper voltage settings are in order. Any distortion of the sound indicates a problem with the voltage.

Welding techniques lacking accuracy and propriety


Apply a push technique (using a forehand motion) to make a bead shape that is flatter than the one made by a (not recommended) backhand or pull technique. Keep the push angle to 5-10 degrees.

Insufficient voltage at the arc due to defective/inadequate/worn work cable


You may experience an overheating work cable. Even worse, the bead shape may not be proper. Use an appropriate chart to determine the right size considering the current and length. For longer distance and higher current, larger work cables are suitable.

Fusion and Penetration Problems: 3 Examples and Solutions

Incomplete fusion and excess/lack of penetration require welding professionals to have very specific MIG welding troubleshooting skills.

#1 Lack of Fusion in Welding

An incomplete fusion or cold lap occurs when no proper fusion between the weld metal and the base metal happens. An incorrect angle of the MIG gun is the typical cause.

  • Keep the stringer bead close to the right point of the joint. Now, widen the groove or adjust your work angle as you see fit to access it completely.
  • Place the arc on the welding puddle’s leading edge by maintaining 0°-15°angle.
  • Hold your arc momentarily on the groove sidewall while following a weaving technique.
  • Increase the welding current/travel speed in case the welding puddle precedes the wire farther.
  • Adjust the speed of the wire feed or choose higher voltage ranges if insufficient heat is the reason behind the cold lap.
  • Keep the base metal’s surface clean and free of contaminants.

#2 Excessive Penetration

Weld metal may melt through your base metal and hang steadily beneath the weld. It’s called excessive penetration, and heat input in excess can be the problem.

  • Keep the voltage range lower than what caused excessive penetration.
  • Reduce the speed of the wire feed.
  • Choose higher travel speed.

#3 Lack of Penetration

Heat input is insufficient, can be the cause of poor or lack of penetration. It may also cause improper fusion between your base metal and weld metal.

  • Increase the speed of the wire feed.
  • Keep the voltage range higher or reduce the travel speed.
  • Prepare the joint appropriately so that you can access the groove bottom and maintain the arc and stick-out features properly.

MIG Weld Defects: 6 Weird Examples and Solutions

While the above problems are common in MIG welding, the following ones aren’t rare either.

#1 Brittle Welds

Incorrect sizes of electrodes or the bare ones cause brittle welds that usually don’t hold up. The welds have to be ductile.

  • Use arc electrodes that are shielded.
  • Don’t use excessive current.
  • Pass over your weld more than a few times.

#2 Cracks

When you see cracks, you want to spend more time in preventing than in fixing them because that’s the easier way.

  • Clean, debur, file, and grind the edges of the plates to allow them to fit together properly.
  • Reheat all sides of the joint at the correct temperature.

#3 Deformation

Deformation is the result of improper welding sequence, thin beads, and/or insufficient clamping.

  • Weld the joint from both sides and the center out (using opposite directions).
  • Use a clamp firmly and choose a large electrode.
  • Change the weld sequence and the joint location as required.
  • Try to complete fewer passes.

#4 Slag Inclusions

Sometimes, small flux particles get trapped inside your weld metal and prevent the weld penetration from being complete. That’s when inclusions of slug occur.

  • Use flux-coated consumables that are maintained properly.
  • Use correct settings and positions for the arc, current, and voltage.


When molten material droplets are created near the welding arc during a GMAW process, it’s a spatter.

  • Reduce the arc length and welding current while having your torch-to-plate angle increased.
  • Check and correct if the flow rates, polarity, and shielding gas type aren’t right.
  • Clean the gas nozzle.


Too high voltage or too long arc can be the cause. Use of the wrong electrode with too long a size or incorrect angle is also considerable. Fast travel speed may also cause undercuts.

  • Check the welding speed.
  • Check the amount of weave being used.
  • Don’t hold the electrode anywhere close to the vertical plate as you’re creating a horizontal fillet weld.
  • Choose the right size of an electrode.

5 MIG Welding Problems and Solutions: The Machine and Other Components

Apart from the welding difficulties and issues in critical parts, things might go wrong with the machine itself or some other welding tools.

Welding Machine Not Switching off

AMIG welder may not go off until being unplugged from the power supply. A deadline switch should be the cause.


Replace and the line switch. If it still persists, check the connection and repair it if required.

Machine Not Starting

Power circuitry if becomes dead may cause the machine not to start. Overloading, wrong voltage inputs or blown-up fuse may also cause this.

  • Check the line switch and voltage input.
  • Leave the machine for cooling off if it experiences overloading sessions.
  • Replace any blown a fuse.

Malfunctioning Ground Clamp

The ground clamp may suffer from heavy oxidation.


Keep the ground clamp clean and free of oxides

Electrical Shocks Received from Touching the Welder

If you fail to ground the frame of your welding machine properly, you may feel electrical shocks, too dangerous to risk!


Follow the user manual, which came with your welding machine for the right grounding procedure.

Dead Polarity Switch

A worn switch or the use of one with the welder under load may lead to a dead polarity switch.

  • Replace the switch.
  • Avoid using a switch with the welder under load.

How do you feel as you’ve just finished our MIG welding trouble shooting guide? Are you now confident of handling the job with all its problems resolved? If you’re, our labor to create this for you will be worth it. Feel free to let us know what you think. Happy welding!

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