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Bobcat 225 NT died and will not do anything

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  • bros1964
    started a topic Bobcat 225 NT died and will not do anything

    Bobcat 225 NT died and will not do anything

    Yesterday I was using my Miller bobcat 225 NT as a generator, I had it hooked up to the meter loop of a shop I am building to check some electrical wiring I installed prior to getting electrical service. While actualy making sure some equipment worked in the shop, the Miller Bobcat died (no sputtering or hesitation it just died) while running at high idle, the machine would not do anything when I attempted to start.

    The battery is new, I have not checked because it was raining last night when this happened. The fuel tank is full and the oil level is good.

    Could this be a fuse, I read that the F-6 fuse when blown the welder would not start. Whould the blown fuse cause the machine to die and not even turnover?

    I need help?

  • killerwelder21
    replied
    I've got something similar to this and it want let me post a new thread so I'll put it here.. please help
    Really need some help on this one, yesterday I welded with my bobcat 225g plus for several hours with no issues, this morning I come out to continue my work and I went to start it and it tred to start 4 or 5 times but was having a hard time due to a dead battery but I had it on a charger, and after a few try it just stopped, now when I turn the ignition switch to start it doesn't do anything, it doesn't click, doesn't spin, it's like it doesn't even have a battery. I checked the oil it was about a half pint low, filled that, it's full of fuel, this machine has a little under 1800 hours on it. What could cause it to do this? I've read maybe a f6 fuse but I don't know why it would blow when all I was doing was trying to start it..??

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  • duaneb55
    replied
    Fantastic. Thanks for the follow up.

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  • bros1964
    replied
    Replaced the D-4 Diode Board and the welder is working fine. Thanks for all your help.

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  • bros1964
    replied
    Checked the SR2 and D4, the SR2 checked out ok the D4 was bad. Waiting on parts. I will let you know when I get parts how it turns out.

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  • bros1964
    replied
    Thank you sir, I will try testing the rectifier and the diode board this evening. I will let you know what I come up with.

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  • duaneb55
    replied
    Sounds like bridge rectifier SR2 is bad and you're only getting battery voltage (initial exciter current) at the brushes. If you're unsure on how to test SR2 with a VOM (diode setting) - google is your freind.

    You'll also need to check D4 the same basic way and I wouldn't doubt it's shorted which would explain the blown F6.

    Leave a comment:


  • bros1964
    replied
    Thanks Cruizer, I tried a regular glass fuse, still have weak weld output. The machine speeds up when arc is struck but not enough output to keep arc. Does anyone have any advice on what to check next? I realy need to get this machine running. Thanks for the help.

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  • cruizer
    replied
    Originally posted by bros1964 View Post
    Well I pulled the top off this evening and the F1 Fuse is blown, duaneb55 what is the best way to check the D4 and the SR2? I know that I need to check resistance with a ohm meter but not sure how I need to do. Also it takes a while to get parts around here, does anyone know if I can get a aftermarket fuse and also the best place to order parts online?
    Well, just stick a simple glass fuse in it, a Electronics store will have the ceramic version, a gas station will have the fuse. Don't worry bout the voltage on the fuse, an amp is still an amp. It'll blow all the same.

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  • bros1964
    replied
    Well I pulled the top off this evening and the F1 Fuse is blown, duaneb55 what is the best way to check the D4 and the SR2? I know that I need to check resistance with a ohm meter but not sure how I need to do. Also it takes a while to get parts around here, does anyone know if I can get a aftermarket fuse and also the best place to order parts online?

    Leave a comment:


  • duaneb55
    replied
    After checking the engine harness plug, I'd check fuse F1 that you've suggested and flashing diode D4 mentioned in post #3 and exciter current rectifier bridge SR2.

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  • cruizer
    replied
    You really want to inspect the harness plug inbetween the engine starter and generator section. It's VERY likely that the terminals have turns green from corrosion. Clean them and either spray them with the likes of WD-40 or use a DI-Electric grease.

    This is your most likely culprit.

    Leave a comment:


  • bros1964
    replied
    I appologize for not getting back and letting everyone know what I found. I found the F6 fuse blown and replaced, the machine fired up when I attempted to strike an arc the machine reved up as usual and I assumed that it was fine. A few days ago my son attempted to use the machine and it would barely strike when attempting to strike an arc. I assume the F1 fuse is blown also, while I am in there are there any suggestions on what to look at also?

    One thing I failed to mention in my original post is that it was raining the night the machine quit, is it possible a short was created due to rain? Thanks for the help to this point.

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  • cruizer
    replied
    I have my doubts that he is going to report back, most never do.

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  • duaneb55
    replied
    I did consider the dumping of a heavy auxiliary power load while testing could result in a spike of exciter voltage which could take out (short) flashing diode D4 and backfeed the battery circuit thus blowing F6.

    But as you know, F1 should blow first if such were to happen so . . . ???

    I agree "a dead battery, non charging, or low oil would not take that fuse out" but a bad regluator could and I wouldn't rule out a battery/ignition circuit wire shorted to ground either.

    I too am curious as to what the OP finds.
    Last edited by duaneb55; 09-18-2012, 08:24 PM.

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