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Discussion Starter · #1 ·
Hi,

I've read through the thread about the dash cam install by "tk1971".
However, his car is a Premier, mine's an LT. The harness in the mirror is different. In his thread, he mentions that the purple wire is ignition and black is ground.

This is what mine looks like. How do I find out which of the wire is ground and which is the switched (powered on when ignition is turned on)?
My harness doesn't have black, or purple. Each wire has 2 colors.

Thanks,

 

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One way to find out is by sticking a needle into the back of the connector and use a voltmeter. Hopefully someone has done this already to save you the time.
 

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Discussion Starter · #3 ·
One way to find out is by sticking a needle into the back of the connector and use a voltmeter. Hopefully someone has done this already to save you the time.
Will this do the job? I asked a friend about my situation, and he gave me this. He's on vacation, so can't ask him any more questions for now.
Thanks,

 

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Will this do the job? I asked a friend about my situation, and he gave me this. He's on vacation, so can't ask him any more questions for now.
Thanks,
Yes, that's what you'll need. Although, usually you have the black wire in the common. You can ground the common on any metal part of the car. And use the 20VDC setting to look for 12VDC with the red wire probe. To find a ground wire, if there is one, by using the ohm setting to look for continuity with any metal part of the car. You can test the meter's ohm setting by touching the probes together and it should read zero.
 

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Just a couple clarifications. I should have said a multimeter instead of a voltmeter. Multimeter can measure more things then just volts. It looks like from your picture you can just unplug the connector and test the contacts directly. Trying to stick a needle in the back of the connector can be a PITA.
 

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Discussion Starter · #6 ·
Yes, that's what you'll need. Although, usually you have the black wire in the common. You can ground the common on any metal part of the car. And use the 20VDC setting to look for 12VDC with the red wire probe. To find a ground wire, if there is one, by using the ohm setting to look for continuity with any metal part of the car. You can test the meter's ohm setting by touching the probes together and it should read zero.
So to find which of the 5 wires is "ignition switch", I'll first switch the positions of the black and red probes (meaning, to plug black into common", then touch black probe to a metal surface in the car, while touching red probe in each of the five wire slot, (while turning the car on of course)? What should the number on the readout be?

Thank you!
 

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So to find which of the 5 wires is "ignition switch", I'll first switch the positions of the black and red probes (meaning, to plug black into common", then touch black probe to a metal surface in the car, while touching red probe in each of the five wire slot, (while turning the car on of course)? What should the number on the readout be?

Thank you!
If typical power, it should read around 12 volts. Could be higher depending on the 12 V battery charge, which could be nearly 14 V.
 

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And the ohm reading should be around zero when looking for a ground wire?
Thanks,
Correct. My old analog multimeter let me adjust zero by holding the two probes together. I haven't used the digital ones enough to know if they have a way to adjust the zero. You can easily test it by holding the probes together while you have it on the 200 ohm setting. A ground should give nearly the same reading as holding the two probes together. Should be less than 5 ohms.
 

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Discussion Starter · #12 ·
So here are the results of my testing with the multimeter.
Dial turned to 20 DCV, black probe against a metal screw in the door, red probe touched each of the 5 wires. Only the black/blue wire showed zero. The other 4 wires each showed anywhere from 5.81 to 5.90. Does that mean that there's not enough voltage in any of the wire to power the radar detector? If so, I'll have to run a cord to the fuse box. I'd rather not use the cigarette lighter for power due to the cord being in the way.

Thanks,
 

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So here are the results of my testing with the multimeter.
Dial turned to 20 DCV, black probe against a metal screw in the door, red probe touched each of the 5 wires. Only the black/blue wire showed zero. The other 4 wires each showed anywhere from 5.81 to 5.90. Does that mean that there's not enough voltage in any of the wire to power the radar detector? If so, I'll have to run a cord to the fuse box. I'd rather not use the cigarette lighter for power due to the cord being in the way.

Thanks,
Have a feeling that's power from OnStar module. Here's a another website forum discussing the 5V from OnStar module: http://forums.genvibe.com/phpBB3/viewtopic.php?t=41772
 
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