Thread: M2-atx hard off when turning ingnition off

I'd like to add my complaint about this issue to the thread. I have everything connected as described in the M2-ATX manual. I'm running jumper B as suggested in the manual. I have all my settings in Windows 7 set to Sleep mode when Power Button is pushed.

When I start the truck, the PC starts up fine. When I turn off the ignition, the PC powers off hard and then starts up again. Then about 5 seconds later, the computer shuts off again.

Is this a defect in the M2-ATX? I read something about polarity of the power switch in another forum, could this be the culprit? Has anyone found a solution for this issue?

I put a 1N4001 diode in circuit in the ACC line and now everything works perfectly. I'm not sure that it's telling the computer to "shut down" (hibernate as per configuration) because my monitor also shuts off upon ignition-off, but when I start the car up again, it boots from hibernation mode ("resuming windows") and that's pretty much what I was hoping for, instead of the "hard-off" that I was getting before upon ignition-off. Thanks for the tip!

I have a slight variation of this hard shutdown problem with the M2-ATX. At first my problem appeared to be random, in that sometimes it would hibernate and sometimes it would hard shutdown when the ignition was turned off. After a bit of repeated testing, I noticed that it would only ever hibernate after a "fresh" startup when the power harness was completely disconnected (ie all12V power removed). After that, turning the ignition on, waiting for boot, then turning ignition off, would result in a successful hibernation rather than a hard shutdown. Every subsequent ignition off resulted in a hard shutdown, until I disconnected the power harness from the back of the system again.

Next I unplugged all the USB devices from the system, and lo and behold, successful 100% hibernation every time ignition was turned off.

Culprit -> Dlink DBT-122 Bluetooth dongle.

Remove that from the system, and no more hard shutdown problems.

Anybody seen problems with USB / bluetooth devices and the M2-ATX like this before? It's almost like the bluetooth device is preventing hibernation, except it does hibernate after the power harness has been disconnected and reconnected

OK forget the last post. Problem is intermittent. The BT dongle was a furfy.

What made the problem less intermittent and caused the hard shutdown 100% of the time was I had a charger connected to my battery while I was installing / testing. Clearly, as the ignition was switched to off and the charger kicked in and took the load, this sent some sort of spike through the system too. Remove the charger and the problem became less intermittent.

Checked the wiring diagram for my Toyota Prado, and yes I do have a relay on the acc line - it switches on the extra power outlets in the Prado. So I'm off to try a 1n4001 diode.

Just a question about diode placement. Should I connect it between the ACC control line and the ground line at (or near) the M2-ATX, or does it have to be near the offending relay?

OK. just did a test by physically removing the power relay for the extra outlets from my fusebox. Success!!!! Switched ignition on and off about 50 times with not one single hard drop on the M2-ATX.

Put the relay back in, hard drops again on the M2-ATX.

Big thanks to Catatung for finding the exact problem with M2-ATX here (at least in my case). The external relay is definitely introducing kickback that this power supply does not like at all. It's something the guys at mini-box need to hear about so they can improve the design of this PSU. It makes sense now why relays and filters on the control line to clean it up have also solved this problem.

Put the rectifier diode in - anode to ground, cathode to +12V in parallel with the relay. All good, no more hard shutdowns.

Originally Posted by rocksteady

Put the rectifier diode in - anode to ground, cathode to +12V in parallel with the relay. All good, no more hard shutdowns.

I'm experiencing the hard shutdowns as well. My switched line is hooked up via an "add-a-circuit" to my fuse panel. I used a fuse that's for my hvac and it supplies 0v when off, +12v when in acc, and +12v when ign. I also wired in a switch. When using the switch, all works perfect... hibernates and resumes properly. When i turn off the ignition it hardoffs. I also ocassionally see the bios logo just after it shuts down and before the screen turns off.
would installing a diode be beneficial to me? would it hurt if it wasn't the correct solution? If not, do I just run it in parallel with my line after the fuse? or jump it from my switch line after the fuse to my ground?
Any help would be appreciated, as you can tell, I'm no electrical genius.
thanks!

It won't hurt, unless you wire the diode in the wrong way, as that would short +12v to ground, so be very careful with the polarity of the diode. You can put it anywhere between the cable that goes to J3 and ground. It just needs to be in parallel with any potential relay you may also have on that 12V line after your acc switch.

The other way I proved it was a relay that was the problem was to check the wiring diagrams for my vehicle, then just popped the relay for a test.

BTW, I reported this problem to mini-box, and they are looking at verifying the issue.