May want an electrician if not yourself to help you out. I'm sure you know 240V is not something to take lightly! No pun intended.
Since you are using AC and having trouble striking an arc, now check the AC open circuit voltage where the cables hookup. Should be about 75 to 80 volts AC though the entire switch positions. If good voltage level then bad connections or high resistance somewhere when trying to strike an arc.
If low then could be a worn out transformer, provided you have a good stiff 240V source.
Check for 240V on the primary even when striking an arc. Leave the AC voltmeter hooked up to the source and stick the rod to see if your source is stiff!
If that's good and good connections, good front panel power switch, cleaned secondary switch contacts for setting the current, and good as new cables and lugs, then you may have melted wire insulation in the transformer itself.
Like others say, the source should have 2A of idle current with open circuit electrode. The idle current may be higher if the primary has shorted windings. May not see a difference if the secondary has shorted windings but will see a lower open circuit voltage on the secondary.
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