Confused about 12 volt wire splice

[Rykertest]

Hello. I’m in the final stage of adding a 12 volt usb adapter to my 08 Tundra. The mount and usb adapter came with no instructions. I have a red and black wire coming from the new usb plug but the cigarette lighter wires are different colors as you can see. I THINK the black wire goes to the black striped wire already in the vehicle and the red to the white. I have two splice connectors to accomplish this but I wanted to double check here first to avoid making a stupid mistake.
Thanks for your assistance.

 

[Rand]

Use a multimeter and figure out which is the ground and hot.
hot to ground will show voltage
ground to ground will not.

 

[Rykertest]

Use a multimeter and figure out which is the ground and hot.
hot to ground will show voltage
ground to ground will not.

My brother has my multimeter so I guess I’ll have to wait until next week. Dangit!

 

[ripcord]

My brother has my multimeter so I guess I’ll have to wait until next week. Dangit!

I first read this sentence as "My brother was my multimeter..." and had this image of a little kid sticking his tongue out as you touched wires to it, looking for the hot wire.

A test light would work as well, BTW. If you don't have one, you can improvise one with a automotive bulb.

 

[Rykertest]

I first read this sentence as "My brother was my multimeter..." and had this image of a little kid sticking his tongue out as you touched wires to it, looking for the hot wire.

A test light would work as well, BTW. If you don't have one, you can improvise one with an automotive bulb.

lol, well, he’d probably agree that he was the multimeter as well but he’s a drama queen.

 

[bunnspecial]

Harbor Freight also sometimes has a coupon for free DMMs with a purchase, and they have some cheap options.

As I sit here periodically watching .1mv changes on a ~12V device on my HP 3478a(5 1/2 digit lab grade multimeter) I have to grudgingly admit that the cheap HF ones are surprisingly good. They certainly will tell you if a wire is positive or negative, and if the voltage is in the range it should be. The cheapies I have agree with my high end bench meters to the resolution they're readable.

 

[Rykertest]

Harbor Freight also sometimes has a coupon for free DMMs with a purchase, and they have some cheap options.

As I sit here periodically watching .1mv changes on a ~12V device on my HP 3478a(5 1/2 digit lab grade multimeter) I have to grudgingly admit that the cheap HF ones are surprisingly good. They certainly will tell you if a wire is positive or negative, and if the voltage is in the range it should be. The cheapies I have agree with my high end bench meters to the resolution they're readable.

I wish I had a HF closer but it’s two hours to the nearest one for me.

 

[bunnspecial]

I wish I had a HF closer but it’s two hours to the nearest one for me.

If you wanted one, something like this is probably fine too

Amazon.com

 

[Chris142]

Harbor Freight also sometimes has a coupon for free DMMs with a purchase, and they have some cheap options.

As I sit here periodically watching .1mv changes on a ~12V device on my HP 3478a(5 1/2 digit lab grade multimeter) I have to grudgingly admit that the cheap HF ones are surprisingly good. They certainly will tell you if a wire is positive or negative, and if the voltage is in the range it should be. The cheapies I have agree with my high end bench meters to the resolution they're readable.

yep the HF meters are definatly good enough for what hes doing. A $2 test light will work also.

Rykertest... Those scotch lock connectors are the worst.I will even say that they are worse than just shoving a bare wire into a connector and plugging it back in

 

[ripcord]

Twisting the wires together and wrapping with tape is as about as good as the scotch locks.

 

[Nukeman7]

Can you visually trace the white wire and white/black stripe wire back to the cigarette lighter? If so, the wire feeding the center contact on the cigarette lighter is the positive (+) wire. That is the industry standard designed to minimize the possibility of shorting out the electrical circuit due to inadvertent contact grounding of the outer rim of the cigarette lighter receptacle. The same electrical code criteria applies for incandescent bulbs lamp receptacles in your home.

OK, I just looked it up for you. The gray wire is positive (+) and the white/black stripe wire is negative (-) to battery ground. As such, connect the red wire to gray and the black wire to white/black stripe. Wiring schematic is shown below.

 

[Rykertest]

Can you visually trace the white wire and white/black stripe wire back to the cigarette lighter? If so, the wire feeding the center contact on the cigarette lighter is the positive (+) wire. That is the industry standard designed to minimize the possibility of shorting out the electrical circuit due to inadvertent contact grounding of the outer rim of the cigarette lighter receptacle. The same electrical code criteria applies for incandescent bulbs lamp receptacles in your home.

OK, I just looked it up for you. The gray wire is positive (+) and the white/black stripe wire is negative (-) to battery ground. As such, connect the red wire to gray and the black wire to white/black stripe. Wiring schematic is shown below.
View attachment 211213

Awesome! Thank you so much. I found some heat shrink marine connectors in my toolbox I’ll use vs the crimp on. I assume that would be a better choice? Thanks for everyone’s assistance.

 

[Chris142]

Twisting the wires together and wrapping with tape is as about as good as the scotch locks.

better than a scotch lock!

 

[meep]

Home Depot, Lowe’s, Ace hardware all have multimeters, and they start at reasonable prices like $20 and go up from there. I used a $10 radio shack “pocket sized” MM for *years*, slightly larger than a business card, with permanently attached leads. You can get a lot of use out of a cheaper meter.

 

[AandPDan]

Try a fuse tap. You won't need to cut into your vehicles wiring or damage it in any way. You can also fuse the USB adapter to its own rating.

 

[f355spider]

Harbor Freight also sometimes has a coupon for free DMMs with a purchase, and they have some cheap options.

As I sit here periodically watching .1mv changes on a ~12V device on my HP 3478a(5 1/2 digit lab grade multimeter) I have to grudgingly admit that the cheap HF ones are surprisingly good. They certainly will tell you if a wire is positive or negative, and if the voltage is in the range it should be. The cheapies I have agree with my high end bench meters to the resolution they're readable.

Same with digital calipers...I bought a cheap $8 one off eBay just to compare with my Mitutoyo and I'll be darn it was very close and repeatable readings. But it is not very smooth in operation...all gritty and sticky. I hear if you disassemble and clean them then relube they work much better...

 

[paulo57509]

Home Depot, Lowe’s, Ace hardware all have multimeters, and they start at reasonable prices like $20 and go up from there. I used a $10 radio shack “pocket sized” MM for *years*, slightly larger than a business card, with permanently attached leads. You can get a lot of use out of a cheaper meter.

This one?

 

[meep]

This one?

View attachment 211506

Yes!! It was a version of that one!!!

 

[Rand]

Yes!! It was a version of that one!!!

I had one of those too.. but either it eventually died or I lost it in a move.
for this kind of work the free or 2.99 HF multimeter is fine..

 

[RooflessVW]

My brother has my multimeter so I guess I’ll have to wait until next week. Dangit!

All you need is a test light for something like this.