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Thread: M2 PSU ignition/ACC power up problem

  1. #1
    Newbie Bmrbch's Avatar
    Join Date
    Aug 2008

    M2 PSU ignition/ACC power up problem

    I have an M2 PSU powering an miniITX-SN mother board and am having trouble getting the power on ignition working properly. If I turn the key to the ACC line (hooked up to the blue ACC or IGN wire from a wiring harness for my 02 Jeep Gnd Cherokee) the computer boots up great. Or, if I go strait to crank the engine, the computer boots up great. The problem is if I have the computer running on ACC and then start the car the computer reboots. This also happens when I have the car running and I turn it off. Even stranger, if I have the engine off running the computer on ACC and then turn ACC off, then the computer reboots.
    I have:
    Tried multiple jumper changes on the M2 to no avail.
    Rechecked my power wiring (10 guage + and - wire directly to battery and an additional ground wire to chassis ground)
    With the engine and computer running if I disconnect the IGN wire on the M2, everything works as advertized. ('puter stays running till the M2 jumper selected power down is initiated)
    Got a new battery with 850 CCA available

    Sounds to me like a power problem. I thought the M2 should be able to hack it. Any ideas?

  2. #2
    Variable Bitrate
    Join Date
    Mar 2006
    Blog Entries
    I had one power supply that would lock up my notebook whenever I powered off my running engine. To me that suggests there was some electrical noise (spike) that my power supply passed on through to my notebook.

    Switching over to the M2-ATX-160watt power supply and replacing the notebook with a miniITX MB solved the problem for me.

    My guess your car is generating some electrical noise that your power supply can't handle.

  3. #3
    Fusion Brain Creator 2k1Toaster's Avatar
    Join Date
    Mar 2006
    Colorado, but Canadian!
    For the rebooting, are you sure the power button from the M2 to the motherboard is in the PWR button spot and not the reset spot? Happens a lot

    Also in your BIOS what do you have wake from power failure set to?
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  4. #4
    Newbie Bmrbch's Avatar
    Join Date
    Aug 2008
    Definitely have the power button connected to the correct pins (not sure the polarity, but it's to the pwr pin). The thing that makes me think that is not it is that if I disconnect the IGN wire manually everything works like a champ. That's what makes me think it's a pwr problem. Isn't the M2 supposed to be good at that. Any idea on how to try to soften the blow if you will of the power cycle. And would such a thing happen if I just turn from ACC running computer directly to off... that shouldn't give too big a spike, or would it?

  5. #5
    FLAC WuNgUn's Avatar
    Join Date
    Sep 2007
    Probably an issue with the M2 itself. They are a very buggy PSU (M4 as well)... When did you buy it?

  6. #6
    Newbie Bmrbch's Avatar
    Join Date
    Aug 2008
    Bought it in October 08 (bout 2 months ago).

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