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1970 Miller big 40 will start up but won't weld any help out there

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  • 1970 Miller big 40 will start up but won't weld any help out there

    My 1970 Miller big 40 will start up and run but won't weld now. Just got done doing some work to the motor but didn't really touch the generator side of it except that I put a new range selector switch in it. Not sure what's wrong was welding before got the switch with the welder old 1 was really lose so put the new 1 in. Not sure what I could have done to cause it not to weld any help would be appreciated thanks

  • #2
    Well, if the unit was working before the switch, and now it doesn't, it might occur to you that you did something wrong.

    Needless to say, I can't help you


    • #3
      Ok thanks. Anybody else might know what may cause a machine to run but not weld.


      • #4
        Originally posted by jwd_88 View Post
        Ok thanks. Anybody else might know what may cause a machine to run but not weld.
        The advice given before was sound.

        If in fact the machine was working properly prior to any work being done and immediately after the work was done it fails to function a strong suspect would be the newly installed part.

        Now if the machine was welding fine a year before the new switch was put it and was not tested just prior to the switch install, there is a good chance of something else gone wrong.

        I have no knowledge of the machine you speak of, but do have over 35 years experience troubleshooting and repairing electrical/electronics problems.


        • #5
          What kind of work did you do to the motor?

          Was it removed from the unit for the work to be done?


          • #6
            I'd start by double checking the selector switch wiring comparing what you have to what is shown in the manual wiring diagram or any diagram you may have on the inside of the machine.

            Do you have a unit SN instead of just that it's a 1970?


            • #7
              No the motor was left in the machine for the repairs. I replaced the oil pan gasket. Pulled the head to remove the distributor due to the fact it was stuck in place. Replace distributor so timing might be of some which would mean I'm not getting the correct RPM's. I rewired the starting and charging system following the diagram I have. Then I replaced the selector switch and that's it. The machine is a 1970 Miller big 40 gas operated serial number 70 dash 543296 stock number 900 955. The motor is a f163 4 cylinder Continental thanks for the feedback guys.
              Last edited by jwd_88; 11-22-2012, 02:33 AM.


              • #8
                Not sure why I bothered to ask you for the unit SN as I knew it was too old to download the manual from the Resources section.

                So, can you post a good quality photo of any wiring diagram you may of the unit? I need to confirm something before making my next suggestion.


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