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Bobcat intermittent output

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  • Bobcat intermittent output

    Great information here!!
    I have a Bobcat 225G plus serial # KF881886 with 360 hours
    Machine was stored outside for the infamous "year or two"
    Using other post on the forum I got it running, generating, and welding but...
    Testing it multiple times over several days, it always runs but may or may not weld. When it doesn't weld the 120 AC receptacle reads around 2.5 volts. The next start all may work fine, good arc and 120 volts. It either works on startup or doesn't. Letting it run doesn't seem to matter.
    I've checked fuses F1 & F2, cleaned slip rings, brushes are free, cleaned and checked variable resistor on the bulkhead.
    Any suggestions on what could be failing and how to test?

  • #2
    Check the selector switches. Probably corrosion on the contacts giving intermittant connection. Switch from AC to DC and back several (dozen) times, move the rheostat from one side to the other several times, turn the voltages up and down several times.

    You can also spray the contacts with a good contact cleaner.

    My guess.


    • #3
      I have found that when you have low output and no or low aux.power it is usually a grounding problem. The connection for the electrical grounds inside the machine where all the grounds termanate at the frame. Remove the screw and clean the area to bare metal. Make sure all your electrical connectors are not corroded and reconnect them. After you reconnect them you can give the area a shot of sealant, (I usually use paint).


      • #4
        Thanks for the info. I'll print this for reference!


        • #5
          Thanks Guys An update
          I rotated the switches (many times) and cleaned ground, no affect.
          Haven't got contact cleaner yet. Any suggestions for brand? Have most of the major auto parts stores near.
          Since trying the suggestions with no output I started it again and watched the AC voltage closely. It started at 2.7 and over a minute or so gradually went to 119.
          I waited a couple of hours and tried again. Started at 2.7 and did not change. Turned off after 5 minutes.


          • #6
            Look on the diagram for "C1", might want to disconnect the wires and clean the terminals. This is your likely culprit. That or you've got a stuck brush. Either one or the other....
            As for the selector switches, I just shoot them with an LPS lubricant, WD-40 will work satisfactory though. I never use contact cleaner on them.


            • #7
              I've used contact cleaner and WD 40 on all switch contacts along with multiple rotations. Removed and cleaned the wire connections on C1 (isn't that the big blue capacitor?). Have pulled the brush holder and brushes move freely, a little WD 40 on them also. Noted that the brush toward the front of the machine shows slightly more wear than the rear one. Output still 2.7 volts.

              Started several more times but only 2.7 volts. Maybe component finally completely failed.
              From other posts I see possible culprits as:
              F1 & F2 - both check for continuity
              Control Bridge - don't see this on schematic What is it and can I check with digital VOM?
              C1 - What is proper discharge procedure and can I check with digital VOM?
              SR2 - found instructions Checks OK
              Thanks again for all the help
              Last edited by kahyes; 05-17-2010, 05:44 AM. Reason: added comments


              • #8
                contact cleaner?

                i've seen contact cleaner at the store and i've also seen degreaser. i don't have contact cleaner but i do have degreaser. are they the same product or not. don't want to harm my machine with wrong cleaner.