Thread: Startup pulse not doing it's thing

[I don't own an m4, so just guessing here]

You can measure the resistance on the two pins of the power supply where you connect the on/off cable - it should drop to 0 for a short period when it's trying to turn on the computer. Note that your multimeter might actually not be fast enough to detect that change.
The computer turns on when you short the On/Off pin. Try attaching wire leads to the mobo on/off pins and shorting them manually. See if it takes an abnormally long time to turn on after you short it (like 2000ms instead of regular 400ms). If that's the case, it might be either a defect of the mobo or some weird BIOS setting.

Have you tried flipping the pin headers on the mobo/m4 and every combination thereof... I had an issue where the m4 pins were switched, took it out, turned it around, put it in, and it worked.

Also, make sure it's in the right pin position on the m4 (I read contradicting statements of the manual vs. forums). The manual had the right positions for mine .

It's definitely not the polarity of the pins. I've tested this in the past to make sure (in the past). Plus, if that were the case, then the shutdown pulse would not work either...but in my case it does.


I forgot to add that I also have a push button switch also spliced into the same wires that go to the MB header. It has always worked and has been part of my system since day one (oh so many years ago)...so shorting the MB headers always works manually with my switch.


When I get some free time this weekend, I will try to see what's happening with the resistance during startup pulse and compare it to the shutdown pulse. If my multimeter isn't fast enough to catch it, I will try a much longer pulse width just for testing purposes.


Thanks for the suggestions so far!

I tried measuring the resistance across the MB header using my multimeter during startup and shutdown and I'm not sure what to think now...

Before I started it up, the resistance was around 1.7K ohms. During startup, it started fluctuating all over the place and then continues to do so until it shuts down. It simply fluctuated between 0 (short) to OL (open circuit) until I shut things down and it then returns to 1.7K ohms after successfully shutting down the PC.

So now I am even more confused as to why it is fluctuating so much when the car is on. I'm guessing that it is changing so fast (and so much) that my meter cannot accurately display what is going on but I suppose it doesn't really matter since it is not effecting the PC while it is on. I just can't figure out why it is not shorting the circuit during startup even though it will short it during shutdown.

As a last resort, I might try to short JP1 in order to reset the M4 back to "default"...but I will need to take apart part of my car in order to reach the pins on the M4 (what a pain)...in the mean time, I'll have to manually turn on my PC every time. :P

Did you ever get a solution here? I am having problems with my zotac h55 and m4-atx. sometimes the pc boots other times it repeatedly turns on and off like i am holding the power button in.

Originally Posted by AhX

Did you ever get a solution here? I am having problems with my zotac h55 and m4-atx. sometimes the pc boots other times it repeatedly turns on and off like i am holding the power button in.

Similar problem. To boot, the fricking power supply doesn't turn off when I disconnect the ground. It was grounding itself through my line out cable. How is that possible????

Is the M4 a complete piece of crap?

Well, I finally had a chance to do some more troubleshooting and I was able to determine that I had a loose splice inside of my PC case (where the push-buttons and the leads to MB on/off pins on the M4). The push button was connected fine (which is why it always worked), but the lead to the M4 wasn't always solid which is why it sometimes worked. Even though it would shutdown every time I sat and watched it, I noticed that Windows would tell me that it didn't shut down properly (every once in a while). What really threw me off was that it never worked during startup (not even sometimes). I guess it's because the loose connection wasn't heated enough like it gets after a while (remember, it's inside the hot PC case). Now that I'm actually at home, I was able solder the wires and do it the right way!

Good ol' thread here, been a while, I might as well chime in.

Good job figuring out your problem! I haven't had my pc in the car for a long time now (well 2 months without it is long for me). I've had my car pc running inside as my desktop, still using the m4 since I didn't want to dissassemble my wiring. I have a relay spliced into the power on/off for the mobo from the m4 so it only gets a signal if the pc is already on. This allows me to have complete control over turning it on, instead of with the ignition. The m4 is jammed in the very back of the case with a single molex connected fan sitting right on top of it, I think blowing down onto the m4. Besides the heatsink and that, no other fans exist for me. It gets very hot and it's been constantly running for 1.5 months straight without being turned off, hibernating, or sleeping.

If everything is connected up fine and working, it's a very competent supply. Despite that, I didn't have to have a ground with it to work in the car. I think my vga extension or "headphone connection" (sorry forgot the size of it, 1.8mm rings a bell) might have been carrying it's ground. Caused my subs to go haywire somehow, but that's the price of not taking your time I guess.

Hope it lasts for ya!

P.S. - NONE of my connections are soldered as I absolutely suck with a soldering gun. All wrapped and electrical taped.