MIG welder not working

[randomeddy]

We have a little mig for general repairs. I left it in a damp shed and now it doesn't work.

It powers up but the light does not come on for the switch. It hums when pressing the trigger but no wire comes through.

Any ideas?

[tapkaJohnD]

Left in a damp shed,check the wire feed mechanism (are the rollers rolling?), and that it hasn't corroded the wire inside the torch cable. That will have a liner which may be replacable, if you can find a supplier.

But if it's not some mechanical fault, but an electrical one, leave to an expert!

[Wicker Man]

Has it not been used for a while? I’d remove and clear any weld splatter from the nozzles, slacken the wire tension and pull the wire through a couple of inches with some pliers. Then give it another try.

[randomeddy]

I will have another look, thanks.

[droopsnoot]

I bought a used welder some years ago, that produced very poor welds so I took it to pieces and cleaned up the internal connections which cured the problem. Some of them had quite a bit of surface rust on them, which might be similar to your situation after being in a damp shed. I didn't do any major stripdown, just cleaned up stuff that was easy to get to. If it's a real electrical problem (and not an obvious fuse issue) than as above, best have an expert look at it. I don't think basic MIGs are all that complicated, and I seem to recall the manual for mine has a basic circuit diagram in it.

[randomeddy]

Thanks for all the help.

Is the wire spool driven or does just get pulled through and should rotate freely ( with some tension I know to stop it unwinding.)

[droopsnoot]

I've had three, all fairly low-end, and the wire spool hasn't been driven in any of them - it's the feed rollers that pull the wire off the reel and then push it along the liner. I could imagine issues if the spool was driven - you'd have to slow it down as you worked through the spool, for a start, because the rotation speed on a full spool would produce wire at the torch faster than the same rotation speed with an almost-empty spool, just as your car speed slows for a given RPM in a given gear as your tyres wear down (albeit not by as much).

[Krikkit]

I doubt there are any welders which use direct spool drive, as noted you'd have to vary the RPM by reel size etc, it'd make it way too complicated to get a consistent feed rate.

[sam hill]

It would be impossible to drive the spool to feed the wire, it would just unwind the wire off the spool.

[randomeddy]

Fixed it.

The welding wire had corroded and the machine was struggling to pull it through, plus there was a small issue with the reel possibly caused by me.

Wound out loads to get to a good bit of wire.

Now that I have had had it in bits I can see why I was confused about the spool being driven. Doh.

Thanks for the suggestions.

[tapkaJohnD]

Thanks for the feedback.
Was the corrosion on the reel, on the drive wheels or in the torch lead?

[finishing touch]

randomeddy said:

Fixed it.

The welding wire had corroded and the machine was struggling to pull it through, plus there was a small issue with the reel possibly caused by me.

Wound out loads to get to a good bit of wire.

Now that I have had had it in bits I can see why I was confused about the spool being driven. Doh.

Thanks for the suggestions.

If you pulled rusty wire through the liner then it will be full of rust powder. Blow it through with an air line till clean. Re-assemble.

Blowing the liner through is routine maintenance with a MIG.

[randomeddy]

It seemed to be the actual wire being rusty caused the roller to not get enough of a grip to pull it through.

I was half tempted to buy new consumables for it but for the tiny amount I had to weld/tack I managed.