Troubleshooting guide › Process troubleshooting › ARC / MMA welding problems
Stick welding has the fewest parts to go wrong, which means almost every problem is one of four things: the electrode, the current, the earth, or the operator’s arc length. This page covers the machine-side faults as well, so you can tell the two apart before calling anyone.
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 arc does not have the energy to keep itself alive when the electrode touches.
Pressing the electrode onto the plate instead of striking it like a match, or holding it there after the arc starts.
A damp coating does not ionise cleanly and the arc dies on contact.
High resistance at the clamp drops the open-circuit voltage and the arc cannot establish.
Some basic and cellulose electrodes need 70 V or more OCV to start.
The start pulse that frees the electrode is not there.
| Symptom | Likely cause | What to do |
|---|---|---|
| No arc at all, machine on | Earth not connected; output cable loose; electrode holder jaws worn or insulated by spatter | Check both output lugs, the clamp, and the holder jaws |
| Arc starts then breaks after a few seconds | Supply voltage low or one phase missing; cable too long or too thin; poor earth | Check the supply under load, cable size (at least 35 mm2 up to 300 A, 50-70 mm2 above), and the clamp |
| Arc breaks when the electrode is pushed into the joint | Arc force too low on an inverter; current at the bottom of the range | Raise arc force to 30-60 %; raise current |
| Arc OK, then stops; protection lamp on | Duty cycle exceeded, fan blocked, ambient hot | Leave on to cool; clear the inlets; the job may need a bigger machine |
| Arc roars and wanders at plate ends | Arc blow | See the arc blow page |
| Current cannot reach the set value | Supply voltage low; cable too thin; a diesel generator not at rated speed | Measure the supply; use the specified cable; check generator rpm and fuel |
| Machine humming, breaker trips | Internal fault | Isolate and call service; do not keep resetting |
| Electrode | Used for | Polarity | Storage |
|---|---|---|---|
| E6013 rutile | General fabrication, thin to medium plate, easy slag | AC or DC either; DC- for thin sheet | Dry store; re-dry at 100-120 degrees C for 1 h if damp |
| E7018 low hydrogen | Structural, thick plate, high-strength steel, crack-sensitive joints | DC+ (AC on AC-rated types) | Bake 300-350 degrees C for 1-2 h, hold at 100-150 degrees C; use within 4 h of the oven in humid weather |
| E6010 / E6011 cellulose | Pipe root passes, dirty or rusty steel, vertical-down | DC+ (E6011 also AC) | Do not bake; keep dry at room temperature |
| E308L / E316L stainless | Stainless to stainless; E309L for stainless to mild steel | DC+ | Bake 250-300 degrees C for 1 h; keep in the holding oven |
| Hardfacing and cast iron (nickel) | Wear parts; cast iron repair with short beads and peening | DC+ usually | Keep dry |
Baking temperatures vary by brand; follow the figure on the electrode packet.
Polarity: for DC, “electrode positive” (DC+ or DCEP) puts more heat into the electrode and gives deeper penetration with most electrodes; “electrode negative” (DC-) puts more heat in the work and suits thin sheet with rutile electrodes. The holder goes to + for DCEP. Swapping the leads at the machine terminals changes polarity; always with the machine off.
| Problem | Usual cause on stick | Page |
|---|---|---|
| Porosity | Damp electrodes, long arc, rusty plate, arc struck outside the joint | Porosity |
| Slag inclusion | No interpass cleaning, downhill, flat angle, low current | Slag inclusion |
| Undercut | Current too high, long arc, wide weave | Undercut |
| Lack of fusion | Current low, large electrode in position, slag ahead of pool | Lack of fusion |
| Cracks next morning | Hydrogen from damp E7018, no preheat | Cracks |
| Spatter | Long arc, current high, damp electrode, arc blow | Spatter |
| Arc strikes | Striking on the plate | Arc strikes and crater cracks |
| 3 mm sheet | 2.5 mm E6013 at 60-80 A, DC- or AC |
| 6 mm plate, fillet | 3.2 mm E6013 or E7018 at 100-130 A |
| 10 mm plate, multi-pass | 3.2 mm root at 100-120 A, 4 mm fill at 150-170 A |
| 16 mm and above | 4 mm root, 5 mm fill at 190-230 A, preheat if alloy steel |
| Vertical-up | One size smaller electrode, current at the lower end, weave with a pause at each side |
| Arc length | About equal to the core wire diameter |
| Electrode angle | 60-70 degrees to the plate, dragging |
Current ranges are typical; the packet range overrides them.
DC gives an easier, smoother arc and runs every electrode type. AC transformer machines are simpler, cheaper to maintain and immune to arc blow, and run E6013 well. Many shops keep both.
In dry weather up to about 4 hours; in the monsoon, 1-2 hours. After that, re-bake. Damp E7018 gives porosity and hydrogen cracks.
The auxiliary load pulls the engine speed down and the welding output follows. Use the auxiliary power only between welds, or size the set for both loads.
Lamps, fault codes and the checks an operator can do outside the cabinet, for the machines this page applies to.
For E6013 on light work any machine runs. For E7018, cellulose and stainless electrodes a DC inverter with adjustable arc force and hot start makes a visible difference: fewer sticks, fewer restarts, less spatter. On thick magnetised steel an AC transformer machine still earns its place because it does not suffer arc blow. A diesel welding generator should hold its rated current at 60 % duty, not just on paper.
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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