Suggestions on how to troubleshoot mig welder

[rfuerst911sc]

Hey guys I have a Hobart 140 mig welder that has served me well . Last time I tried to use it 2 months ago the drive wheel/motor that pushes the wire was not working . When I pull the trigger there is a solenoid click but no movement of the drive wheel .

Anyone ever have a similar problem ? The nozzle appears to be clear and I don't think the issue is in the hose or trigger hand assembly . Anyone know what voltage the drive motor runs at ? I want to pull the connector that feeds the motor to make sure it is getting power when the trigger is pulled .

Worst case I will call Hobart and see what they say . The welder is in near perfect condition so well worth repairing . Any advice appreciated .

[Rot 911]

Take the tension off the drive wheel and see if that gets it to start moving. Even though you don’t think the wire is jammed in the hose, it might be.

[rfuerst911sc]

Originally Posted by Rot 911

Take the tension off the drive wheel and see if that gets it to start moving. Even though you don’t think the wire is jammed in the hose, it might be.

Yeah I previously tried that . I can take a pair of pliers and physically rotate the drive wheel so it's not locked up . So it's either not getting a signal to turn on or it's getting the signal and not responding .

[john70t]

[caution: Do this this when it is unplugged. There may be residual voltage. I've had a single spark with the trigger off when using. The drive wheel transfers X0,000Vs to the wire I believe and should be considered a power line. This is for a Lincoln135 but yours should be about the same.)

1. Unscrew the shield at the tip with needlenose and clean that end.

2. Take pliers and pull wire through the system keeping the wire as straight as possible. There should only be slight drag overall. Inner sleeve liners do wear out and need to be changed occasionally. Blow everything out with compressed air.

3. Unscrew the idler/tension wheel wingnut and pull wire again. There should be almost no drag. Any drag should be at the wire spool which needs slight tension to keep it from instantly turning into a birds nest. BTDT. That wingnut sets the tension and the spool should turn smoothly.

4. Turn both idler and drive wheels. Both should move relatively freely. Bearings can eventually seize when stored outside. It's possible the drive motor has seized since you are getting a solenoid activation "click" from the trigger but the motor is not turning the wheel.

5. Plug iback n. With the idler/tension wheel disengaged, pull the trigger. The drive wheel should turn with no load on it. Do not touch.

6. Unplug again. Use the wingnut to set the idler-to-drive wheel clamping force. Too little and the wire won't be pushed or your welds will sputter with inconsistent wire feed. Too much and premature wear happens.

[rfuerst911sc]

^^^ I have done all that . With zero tension on the drive wheel when I pull the trigger I get a solenoid type of click but drive motor doesn't turn . Have adjusted the " speed " knob with no difference . I think my next step is to unplug drive motor plug and jump with 12 volt charger to see if it engages .

[john70t]

Trigger is assumed good because of click.
Solenoid could be moving but main contacts shot i.e. no juice into motor.
Speed knob/rheostat (?) could be bunk. OHMs should increase when turning.
Motor could be toast. Do not wire that backwards! Mark the wires.

Is there a fuse or breaker somewhere? Hobart may have a wiring diagram.

[rfuerst911sc]

I know there isn't a visible on the outside breaker or fuse but I will check when I pull the sheet metal cover . Might be something on the PWB . Appreciate the advice .

[Zeke]

Not uncommon on Hobart's. Go on over to a Hobart welding forum.

@John70T, the drive wheel is not supplying power but it has potential in that the wire gets its power at the torch contact and is isolated from the welder by the plastic reel. You can get shocked if you touch the wire or rollers and the chassis at the same time with the trigger pulled.

Yes, there is residual voltage on the wire after breaking contact with the work. You can eliminate this by touching the wire to the work after releasing the trigger.

[rfuerst911sc]

Well it's official ............ I am an idiot 😩 . I finally got around to calling Hobart this morning and spoke with a technician . He nailed it on the first try . Apparently either by accident or intentionally I had set the " voltage " knob between 1 and 2 .

When the voltage knob is in between settings it won't allow voltage connection . There are slight detents at each number . Place the knob in the correct position and voila it works 😁 . This is a first for me , I have used that welder a lot and never made that mistake . Will never make it again either . Hopefully this helps someone in the future .

[Zeke]

19 months w/o a welder is a long time.