Wire Feed Welder Problem

What would cause my wire feed welder to be hot even though the trigger is not depressed? Not full power but enough to arc wire when grounded.

When i bought a little buzz box welder at a yard sale I could not get it to work well. finally checked with a meter they had switched hot and ground. The case was hot while the welder was trying to run on 120 instead of 240.
Bill D.

Perk said:

What would cause my wire feed welder to be hot even though the trigger is not depressed? Not full power but enough to arc wire when grounded.

Click to expand...

Discharge from the caps!

some commercial units have a switch to turn electrode hot all the time (lincoln DC600 for one)

The question contains insufficient information.

Try again with the make and model of the machine added to the question.

I had a Harbor Freight 120v toy MIG that had the wire hot all the time. The switch just controlled gas and drive motor.

Yep...

Perk- when you say 'hot all the time'... it emits a spark the first time you 'touch' it, but can you re-touch and get another spark?

If not, Ken's right- there's capacitors in there, downstream of the rectifier stack- they smooth out the current flow and protect the rectifiers from getting 'bit' by high harmonic content. There'll be a little charge there. My original Hobart Handler does this, no harm.

If, by 'hot' you mean that it'll draw a continuous arc, Kevin's note about it being 'continous on', and Tim's note about cheap imported junk are both probable. All but the worst mini-MIGs will have a power-disconnect contactor. If yours isn't the latter (cheap) type, then the control contactor MAY be partially sticking. You'll know if you have a contactor, because when you pull the trigger, you'll hear the wire feeder, you'll hear the valve open, and you'll hear a satisflying CLACK to indicate that the transformer secondary has been engaged.

Another possibility, if none of the above are true, is that your welder has developed some sort of insulation breakdown between the primary winding, and either the frame ground, or the secondary, or both, and you have a 'leak' occuring between input power and the gun.

Give it a double-touch test, and if it only sparks the first time, no worries. IF it sparks the second, third, and fourth times, call back with make and model number.

It is a older (12 yrs+) Clarke 100EN Turbo. It 'sparks' 2, 3, 4 and beyond times now. It never used to do this as I am the only owner/user of welder.

Has far as contactor, you may be on to something here. Was not welding very well and found contactor had been hot. Contacts all burnt, so I replaced contactor thinking the 'spark' would go away. The old contactor WAS sticking. It welds much, much better now that it is getting full voltage again, but still 'sparks' and melts wire down to tip. Was afraid it may have overheated the transformer or something else to cause the 'sparking'.

I just can't figure how it sparks with the contactor in the open position (trigger not pulled)!

Assuming it is really hot and not just a little spark from the caps then it is one of two things. Either the main contactor is welded shut or the board or relay that activates the main contactor is shot. Sometimes the contacts can weld itself or the triac on the control board blows.

Hmmm...

Well, Perk... if you changed the contactor, and it's not shorting, that means there's something ELSE that's able to make for a closed circuit.

My guess is (and I don't have a schem on the Clarke, so it's a guess) that the welding current cutoff is either controlled on the WORK clamp side, not the gun side of the transformer circuit... OR... there's some sort of short which makes the spool or feeder mechanism 'hot' regardless. This could be something as serious as a shorted transformer (secondary winding shorted to primary somewhere), or a rectifier or snubber capacitor that's fried and shorted...

Or it could be as simple as steel dust accumulating between the feeder mechanism and the chassis... or even a shorted drive motor... where the drive motor's power circuit is energizing the case of the drive motor, hence, conducting through the drive rolls to the gun...

I guess if I were in your situation, the very first thing I would try, is to place a piece of scrap on an insulated surface (i.e. not a welding table- a chunk of plywood, etc) and see if it does it in an earth-ground independant situation. If that resolves it, then your stray circuit involves earth ground reference.

Next thing I'd do, is clip the wire at the spool, remove wire from the feeder mechanism, and see if the gun remains hot with no wire. If so, that means the feeder mechanism's isolation hasn't been compromised.

See where that leads you, and I'll keep thinking.