M2-atx hard off when turning ingnition off

**DarquePervert** · 10-24-2009, 06:33 AM

I don't know how to fix it, but here's something you can do to confirm your theory.

Grab your multimeter (you DO have a multimeter, don't you?) and measure the voltage on the ignition line you used.
- Start with the ignition off. It should be 0v. Watch it for a few min and see if there are pulses of voltage.
- Turn the key to the ACC position. The voltage should go to ~12v and stay there.
- Start the engine. The voltage should drop during cranking and return to ~12-14v (depending on battery quality) and stay there.
- Turn off the engine and put the key in the ACC position. Voltage should drop back to ~12v and stay.
- Turn key to the OFF position. Voltage should drop to 0v and stay there. If your theory is correct, you should see fluctuation in the voltage after the key is turned to the off position.

Good luck.

**tbird2340** · 10-24-2009, 08:08 AM

I'm not using an accessory wire, I'm using an ignition wire so your test results wouldn't be what your asking..

The IGN line doesn't drop during crank like the accessory line does and you don't get any power in ACC, only in ON, crank, and running.

**DarquePervert** · 10-24-2009, 01:58 PM

That's all well and good, but you still should check voltages ont he line that you're using to trigger startup & shutdown with the key in both OFF and RUN positions to see if you're getting voltage fluctuations after you turn the key off.

And Iw as wondering if you have an alarm with starter disable functionality that might be causing the weirdness.
Don't know if it could or would, but just a thought...

**WuNgUn** · 10-25-2009, 08:59 AM

Perv is right...it's clearly the "IGN" wire your using...you need to measure what's going on with it, or find another wire to use...
Did you go to the12volt install bay website like I told you? Did you look up your vehicles wiring harness??

**tbird2340** · 10-25-2009, 09:14 AM

Originally Posted by WuNgUn

Perv is right...it's clearly the "IGN" wire your using...you need to measure what's going on with it, or find another wire to use...
Did you go to the12volt install bay website like I told you? Did you look up your vehicles wiring harness??

Post #29 "My vehicle only has one ign line and the accessory line is a "mux" line so I don't think I can use that."

**mm87** · 10-26-2009, 12:26 PM

im now also having this same issue. turns on fine, shuts off hard.

I just finished installing my setup a week ago and for that week it worked perfectly as its supposed to. i then took my cp out and hooked it up my desktop psu to put the finishing touches on the software and what not. I then hooked it back up exactly as it was in my car then this started.

i have my +,ign,- wired into the radio harness

im thinking the m2s shutdown controller took a crap since i changed nothing about my wiring. hopefully im wrong, but I only unplugged it and plugged it back in when i was done

ive read all posts in this thread but no one seems to have a definite answer to this problem. hopefully someone has figured it out by now?

**WuNgUn** · 10-26-2009, 01:54 PM

I've written MANY bad things about my two M4's and M2....
Get an RMA

**mm87** · 10-26-2009, 02:08 PM

id rather not spend anymore money on this. if it is in fact bad will they replace mine? i bought it 6 months ago

**catatung** · 12-23-2009, 03:16 AM

Hey guys,

I have some information that might help you locate your problem. My problem is similar; I have my computer on the bench, I run it from a 13.8VDC high amperage power supply. I'm using an M2-ATX with a DG45FC Motherboard. The computer works fine, turns on okay, when I remove ACC there is a 5 second pause and then it sends a shutdown pulse and the computer does it's thing. Reconnecting the ACC wire to 12 volts brings the computer back up.

Just today I added a relay in parallel with the ACC wire. This wire is to disconnect the power line going to my screen immediately when ACC is turned off. Since the computer takes some time to hibernate, and I power my screen from the 12V line of the M2-ATX because the supply is much cleaner than the cars 12V. the screen would stay on until it finished hibernating and the power supply actually turned off. My design has the ACC line trip a relay which completes the connection from the LCD to the 12V line on the power supply. When ACC is turned off, the connection to power the screen is immediately cut and the screen turns off.

Well when I added the relay, when I remove ACC the computer hardoffs and then turns back on a few moments later. I disconnected everything except ground to the relay trigger and the ACC line to the relay trigger. The output terminals of the relay are not even connected to anything. When I remove ACC power, I hear the relay click off and the computer hardoffs like described above. I remove the relay from the ACC line and the power supply shuts down correctly.

This could explain why some of your people have this issue and some don't. Perhaps certain cars have certain relays on the ACC line also which affect the M2-ATX the same way the relay I am trying to add does. If this is the case and what is tricking out the M2-ATX is the quick fluctuation in voltage, you could try adding a capacitor in parallel with the ACC line to the computer to filter the ACC line some. I will keep you guys posted on here if I find something that fixes this problem. In the meantime I thought I would share my experience and put it out there into the pool of information for everyone to look over while we are all searching for the fixes to our individual problems....

**catatung** · 12-23-2009, 04:14 AM

I've done a little more research and so far I've come up with this possibility. This site: http://www.rason.org/Projects/transwit/transwit.htm explains how to use a transistor as a relay or a switch. It also states:

"However, when using a transistor to turn on a relay coil, it is very important to use a 1N4001 diode reversed biased in parallel with the relay coil as in Figure 3. This is to prevent the kickback voltage in the reverse polarity from destroying the transistor. This reverse voltage occurs momentarily when the normal current stops flowing through the coil. It is good practice to always use a diode when turning on any inductive load."

This leads me to believe that a negative voltage may be appearing for an instant when the relay is kicked off and perhaps the M2-ATX is detecting this and shutting down to protect itself. Perhaps a 1N4001 diode in line with the ACC wire could be the solve to this problem, preventing any momentary reverse voltages from any inductive relays or other components that are wired on the ACC line as well. Maybe some electrical engineers who know from experience can chime in and offer some advice or opinions on this?

I'll keep this thread updated if I find out anything else.