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Old 07-17-2013, 04:27 PM   #1
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Default Really strange power issue with MTX-L

Here's a wierd one. Last night, I shut my car off and when I went to restart it the MTX-L would not power up. I checked the connections and everything is fine. As soon as I connected the USB cable from my DIYPNP to the computer, the MTX-L came on. Unplug the cable, it shuts off. I have not changed any wiring, and this just started at random. The MTX-L is getting power from the unused acc wire from the headlight buzzer, and the ground and signals are coming in through the db15 port on the PNP.

Any ideas as to why the MTX-L only comes on when the PNP is connected to the computer?
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Old 07-17-2013, 04:29 PM   #2
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cause you wired it wrong?
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Old 07-17-2013, 04:32 PM   #3
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why the heck would you not ground it to the car?
also why would you not source a switched power source from the fusebox or cigarette lighter or something that's not a buzzer?
I don't get it
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Old 07-17-2013, 04:35 PM   #4
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so you used the black/yellow wire?
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Old 07-17-2013, 04:38 PM   #5
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Yes, it's worked fine for over a year now. I grounded it through the PNP per recommendation from Reverant, and as far as I know the power just needs to come from any switched source, and that one was unused.

At any rate, it's worked fine for quite some time and began having issues for an unknown reason last night.

Edit: Ben, not Reverant.
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Old 07-17-2013, 06:40 PM   #6
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Default Found the problem



Burned ground wire (wire 2). Now the question is, why did it burn up?
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Old 07-17-2013, 06:58 PM   #7
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what's pin 1? looks like pin 1 and 2 touch.
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Old 07-17-2013, 07:22 PM   #8
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Pin one was actually nothing before. I just moved the ground wire (pin 2) to pin 1.

Edit: Doesn't appear that I fixed anything. I resoldered the joints and still have the same problem. The MTX-L only comes on when I plug the usb cable into the computer.
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Old 07-17-2013, 08:09 PM   #9
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Sometimes I should not be allowed to work on my car. In my haste to get it put back together, after I finished moving wires and soldering connections in the PNP, I forgot to move the ground wire to the no.1 pin on the connector. It works fine now, and has a much closer reading than before which is good, but I still need to figure out why the ground wire burned up.

******* rookie mistakes...
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Old 07-18-2013, 10:29 AM   #10
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ground traces don't usually heat up and break apart like that unless 12v is being dumped into them...

are you jumping SG or GND?
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Old 07-18-2013, 12:37 PM   #11
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Gnd. I was told not to use sg for the wideband.
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Old 07-18-2013, 01:07 PM   #12
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yeah dunno. does your serial port have the 5v jumped over to it?
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Old 07-18-2013, 01:17 PM   #13
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Nope. Didn't see any reason to bring it over.
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