Miller 225NT, WC115a, and 30A. Contactor won't close?
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  1. #1

    Miller 225NT, WC115a, and 30A. Contactor won't close?

    Hi, I've got a Miller 225NT Bobcat running a Miller 30A thru a WC115a with a contactor. Some time ago (years) I started having trouble with the contactor not closing.

    1) I've got the 225 set up per the Miller manual, (course range in wire low, weld process in wire pos., fine control at about #6)
    2) powering the WC115a with the standard 115V plug into the 225NT.
    3) Argon gas.
    4) WC115a is in CV mode, internal jumper is in CV INT. No voltage sensing lead.
    5) Good ground lead. Good work lead. New clean connections.
    6) Using 5356 Aluminum .035 wire, new tip and nozzle.

    Everything is set up like Section 3-10 of the Miller WC115a Operators Manual. "Typical MIG Connections and Settings"

    I haven't tried switching to CC Mode. I have run a buddies same setup off my 225NT set up EXACTLY as mine and it works.

    My problem is the contactor won't close when I attempt to run a bead. I can manually push the contactor closed and jam it there with a wooden handled wire brush. This makes the wire hot all the time and it welds nicely. After about five minutes of this I can remove the wire brush and the contactor will open and close as it should. I can weld for hours and it works like Miller designed it. Come back the next day, its dead and I have to try to electrocute myself all over.

    I'm in the sticks of Alaska so sending the thing out to Miller is not easy, would like to fix it here if I can. Any suggestions would be great. Reed switch? Contactor just bad? Thanks in advance for the help!!

  2. #2
    Join Date
    Sep 2013
    central Wis.

    Re: Miller 225NT, WC115a, and 30A. Contactor won't close?

    I believe you need your fine tune around the maximum to get 115 volts to your weld control. Try plugging into a 110 outlet and see if that solves the problem.

  3. #3
    Join Date
    Mar 2014

    Re: Miller 225NT, WC115a, and 30A. Contactor won't close?

    Replace contactor.

  4. #4

    Re: Miller 225NT, WC115a, and 30A. Contactor won't close?

    I messed with it a bit last night. Switched the WC115a to CC mode and put in a voltage sensing lead. No change but had to try it to make sure. MJD, thanks for the idea, I had honestly completely spaced that out. Easy to get worked up and forget the basics!! I tried several outlets (found a faulty GFCI in my garage, thanks for that, onto the project list). Tried fine adjustment throughout the range and no go, contactor wont pull closed. Jammed the trusty wire brush handle in there and wire lights up, burn about 6" of bead and the contactor starts working. It's like I need to pre-heat my contactor. Yofish, yes, I think you're right. Start by replacing the contactor. I'll keep you posted, Thanks!

  5. #5

    Re: Miller 225NT, WC115a, and 30A. Contactor won't close?

    So I just played with the WC115a some more. I pulled the contactor out of the unit and put 12 volts to it off a car battery. Thing works fine, contact slams out closed. Back to the drawing board. I did find something useful however. Miller or any distributor wants about $350 for a contactor, under any of about six part numbers I've found, alot of them superseded. On mine, under a mounting block I found:

    Curtis/Albright Mt. Kisco NY, Made in England.
    Type: SW200R/434 Volts: 12

    Enter that part number into Google and it'll cost a guy about $100. I don't know if anyone has found that before but it might be worth telling the world about and making a Sticky out of it. Miller might not like it, but I generally don't like giving money away just cause they want more of it.

    If anyone has any ideas about my contactor not getting a signal from the guts of my WC115 I'd love to hear them. Thank you in advance!!!

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