Welding machine servicing and typical faults
Almost everything that goes wrong with a welding set is dust, a loose connection or a consumable. The genuinely broken machine is the rare case, and it is the one worth ruling out last rather than first.
Routine servicing
Blow the dust out. Quarterly in a clean shop, monthly where grinding happens. Unplug the machine and leave it standing for a few minutes first — the capacitors inside an inverter hold a charge after the power is off. Use compressed air at moderate pressure; high pressure drives dust further in and can spin the fan hard enough to damage it.
Check the leads and connections. Bayonet connectors work loose, and a loose connector heats up. Run a hand along the leads and over the connectors after a session — anything warm is a resistance you are paying for at the arc.
Look at the earth clamp. The spring weakens, the jaws burn, the contact area shrinks. It is the cheapest part of the circuit and the most frequent hidden cause of a weak arc.
MIG only: change the contact tip, clean the nozzle, blow the liner through at every spool change — see torch consumables.
The common faults
| Symptom | Look at |
|---|---|
| Cuts out after a few minutes | Duty cycle exceeded, blocked vents, dust-clogged interior, ambient temperature |
| Weak arc at rated current | Earth clamp, cable size, connectors, supply voltage under load |
| Will not strike | Electrode damp, earth clamp, hot-start setting, open-circuit voltage on a long lead |
| Unstable arc, wandering current | Contact tip (MIG), loose connector, dirty tungsten (TIG) |
| Trips the supply | Breaker curve, circuit rating, coiled extension drum |
| Trips the RCD | Damp, damaged lead, moisture inside the machine — a genuine fault, not a nuisance |
The pattern is that most rows point outside the machine. Working from the outside in — clamp, leads, connectors, consumables, then the machine — resolves the great majority without opening anything.
Storage and transport
Damp is the enemy of stored equipment. A machine that has spent a winter in an unheated van needs several hours at room temperature before being switched on, because condensation inside a powered-up inverter is how power sections die.
Coil the leads loosely rather than tightly, and do not hang the machine by its torch. A MIG torch supports its own liner, and a machine hanging from it is bending that liner at the worst possible point.
An inverter contains capacitors charged to several hundred volts that stay charged after unplugging. Blowing dust out through the vents is maintenance; opening the case and probing the board is not, unless that is your trade.
Frequently asked questions
How often should the machine be blown out?
Every three months in a clean shop, monthly where there is grinding dust. Conductive dust inside an inverter is what kills them: it bridges tracks on the board and shorts the power section. Compressed air at low pressure, with the machine unplugged and left to stand — capacitors hold a charge.
The machine shuts down after a few minutes and the fan keeps running.
That is the thermal protection working correctly, not a fault. Either the duty cycle is being exceeded or the air path is blocked. Check that nothing is against the vents and that the filter is clean, then work out the real duty cycle with the duty cycle calculator.
Is it worth repairing an old inverter?
Depends what failed. A fan, a switch, a lead or a socket — yes, easily. The power board on a machine out of production — rarely, because the board approaches the price of a new machine and the diagnosis takes an hour of a technician's time before anyone knows.
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