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Strange M2-ATX problem.

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  • Strange M2-ATX problem.

    I just got my M2-ATX and I love it. It works so much better than my old Carnetix/PW70a combo. That damn thing never stayed on when my engine wasn't running even though my voltage level was fine (plus it couldn't power a PCI video card in addition to the rest of my setup).

    Anyway, on to the problem... at first everything seemed fine with running the M2-ATX without the engine on, but now I am getting a strange problem intermittently. The computer stays running just fine, but the head-unit keeps turning on and off!?!?!?

    I have the HU's ACC like tied to the delay-on on the M2-ATX (to prevent power-on thump). It always works fine with car running, and sometimes with the car off, but other times the HU plays for about 2 seconds, then goes off for 1 second like the ACC line dropped, then it comes back on for 2 seconds again and so on.

    The really strange part is that is seems to stay on if I switch to radio instead of CarPC. Its only when playing audio from the CarPC and then engine not running that the HU repeatedly turns on and off.

    Anyone have any advice?

  • #2
    Is the HU connected directly to the delay on of the M2, or did you use a relay?


    • #3
      Directly. It shouldn't take much current though (probably not more than a relay since the remote out from the HU isn't enough to drive a relay - but it turns on my amps fine). Plus it works fine when the car is started. You really think I have to add a relay? I would think the M2 atx would be able to drive the same little amount of current on the delay-on line weather the battery was at 13.8V (car running) or 11.8V (not).


      • #4
        If your voltage or current is dipping, this will cause your HD to think its suppose to turn off. What I would do is hook up a voltmeter to see if it drops voltage when the HD is powering on and off. If that is the case, you could place a large capacitor across the line to prevent voltage drops.

        It could just be a power draw problem. If your engine is off and you are playing music off of the HD or CD through the Head Unit, then the M2-ATX might not be able to keep the 12V steady, or your battery can't keep the 12 volts. Does this usually happen after a drive, or like in the morning when the car has been off for a while? Also, do you have the amp thump line going to other devices?
        PROGRESS [==========-] 99.9% <- Are we ever really actually done with our carPCs?


        • #5
          I assume you mean HU (Head-Unit) not HD.

          Anyway, I will check out the voltage on the M2-ATX's delay off. Yes, it just goes to the HU's ACC line. The HU then has it's own REMOTE line that goes to the amps.

          A relay might be the answer as long as the M2-ATX can supply enough current to that, but I really don't think the HU's ACC line requires much more than a relay either. I don't understand how the M2-ATX can run my whole PC and LCD for hours with the car turned off, but it can't keep voltage high on the delay-on pin.

          BTW: I have a SLA battery in the trunk, a BatCap-800 under the hood, and a 1.3F cap on the power-distribution block in the trunk (which powers the HU, M2-ATX, GPS active antenna, my 4-channel amp, and my sub-amp). The cap has a voltmeter which always reads at least 11.6V even after running for an hour with the car off, so I don't think I'm low on power here.


          • #6
            yea I meant HU, lol, typing to fast.
            PROGRESS [==========-] 99.9% <- Are we ever really actually done with our carPCs?


            • #7
              A HU's remote line is enough to trigger a relay, or at least it's supposed to be. Most HU manufacturers recommend adding a relay if you're going to connect three or more devices to that output, i.e. two amps and a crossover, etc. I would assume the M2's remote out is similar, so using a relay triggered by this output to turn on your headunit should solve your problem.