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ONAN MDKAW help

Discussion in 'Generators' started by Capt Ralph, Sep 28, 2011.

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  1. Capt Ralph, Sep 28, 2011
    #1
    Capt Ralph

    Capt Ralph Senior Member

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    Were getting error code 3-13 & 27. Genset only runs a few seconds then shuts down.
    Looks like the computer (somewhere) does not see VAC and shuts down.
    I can not find any manuals on-line and the code descriptions do not point to anything.
    Anybody have a gen-end manual or IPB on PDF out there? Any ideals before I pull out the hammer and start poking around with old school adjustments (with hammer)?

    Thx, Ralph
  2. DTW Viking60, Sep 29, 2011
    #2
    DTW Viking60

    DTW Viking60 New Member

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  3. Capt Ralph, Sep 29, 2011
    #3
    Capt Ralph

    Capt Ralph Senior Member

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    The basic error codes break down to; No VAC detected after engine start. Then "Contact Onan for service".
    Looking for the service schematic, logic theory, service manual (Not operators manual) or even an illustrated part breakdown (IPB).
    We didn't win any lotto's and want to at least peek into it smartly before calling anybody else in.

    Thank you for your time but the above linc didn't connect to anything
  4. DTW Viking60, Sep 29, 2011
    #4
    DTW Viking60

    DTW Viking60 New Member

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    Lets Try This, They show several MDK series manuals, which I assume run the same fault codes on all
    If you call up MDKBW, section 5-3, it shows all the fault codes, and how to diagnose them. Good Luck

    Cummins Onan
  5. Capt Ralph, Sep 29, 2011
    #5
    Capt Ralph

    Capt Ralph Senior Member

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    Yep, Same codes, same results. Low or No VAC detected.
    It's not fuel related, engine is up to speed. No A/C electricity detected, then it shuts down.
    The operators manual offers nothing more technical than "check fuel" & "Call for service"
  6. Capt Ralph, Nov 14, 2011
    #6
    Capt Ralph

    Capt Ralph Senior Member

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    Follow up

    I thought I was finding an exciter voltage but it seems the module sends out the first signal to kick the exciter windings off. The module would only let the gen-set run for a couple of seconds and shut down so I was never able to check these signals any further and assumed I was on the correct path, the module.
    Keeping this story short (but painful) it was NOT the module. All of the windings tested good with a ohm meter. I had to dig deeper.
    Peeling past all the sheet metal and pulling the support end cage off, I found a bad diode in the potted diode packs.
    I have heard about bad diodes but had never found one myself. I found one now.
    Is it just bad luck or does anybody know how/why these diodes go bad. I suspect a damp environment may contribute.
    I should have it back together by weeks end. More updates then.
  7. Capt Ralph, Nov 16, 2011
    #7
    Capt Ralph

    Capt Ralph Senior Member

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    update 2

    Diodes did the fix.
    Module sees the exciter at proper op and keeps the gen going. Amazing how that works. I'm still amazed how an open diode fails and keeps a 6 point rectifier down. And still don't know what caused a sealed diode to fail. Did I mention this 11.5 Onan only has 160 hours on it?
    I'm guessing here, can an humid environment, short warm up, medium load applied (2 or 3 A/C units and an inverter charger) cause a diode to fail?