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Thread: Quick 12v question?
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05-16-2020, 12:54 PM #1
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Quick 12v question?
2020 2600rb front side marker light. I have a white and a green wire. I believe the white is -12v and the green is +12v. Is that correct.
Charles and Susan
2021 Ram 3500 Laramie, 6.4 Hemi, 4x4 CCSB
2021 337rls w/ Andersen hitch.
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05-16-2020, 01:44 PM #2
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Not technically the right terms. If you had +12V and -12V you’d have 24V. You sometimes see them referred to as 12V positive and 12V negative, which seems like nearly the same thing but is very different. Best to just say 12V and ground or 12V and 0V to avoid confusion. Color coding on trailers is hit and miss. Always verify with a meter.
John & Kathy
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SW Indiana
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05-16-2020, 01:47 PM #3
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05-16-2020, 03:08 PM #4
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I appreciate the clarification on the terminology. Yes the green is +12v and the white is ground.
Charles and Susan
2021 Ram 3500 Laramie, 6.4 Hemi, 4x4 CCSB
2021 337rls w/ Andersen hitch.
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05-16-2020, 03:12 PM #5
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Not trying to be a smart-alec, sorry if it seems that I am. However you have a better chance of winning a lottery than you do of having this be the last time you'll be working on the electrics of your trailer. You will almost certainly have future electrical problems or projects, and a multimeter is a nearly-essential tool for dealing with them.
The most basic features you'll need are AC and DC voltage measuring and continuity / resistance measuring - these can be had for a few tens of dollars and can tell you in seconds which wire is "hot".
https://www.homedepot.com/s/multimeter?NCNI-5
However you'll be in circumstances where you want to know how much CURRENT is traveling through a circuit (why did a fuse blow, for example) and many of the cheaper multimeters either don't measure current at all or they are limited to about ten amps. Your trailer has 15-amp and 20-amp circuits feeding its AC plugs/outlets inside and has currents of as much as 30 or 50 amps of AC power on its shore power circuit. Most of the DC circuits in the trailer (lights, fans, controls for water heater and furnace) are 15-amp DC circuits. The ten-amp current measurement capability of cheaper multimeters won't be sufficient.
For that reason, consider biting the bullet and spending more when adding this most-basic tool to your road-worthy kit. The "clamp meters" ranging from about $60 to several hundred dollars are better choices. Like this one:
https://www.homedepot.com/p/Milwauke...5-20/202527084
(Note that that one doesn't say anything about including "test leads", the wires with probes that you'll often use to check voltage or continuity. You'll want to be sure you have them, either included or purchased separately.)
Good luck with your projects, current and future.Last edited by boyscout; 05-16-2020 at 03:17 PM.
Mark - 2018 Solitude 310GK - 2017 F-350 diesel SRW short box - Pullrite Superglide hitch
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05-27-2020, 12:08 AM #6
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Hey, did you ever figure this out? I'm installing the Furion Side View camera on my Imagine and failed on the first attempt. Original marker light has 2 white wires and then 1 green and 1 green/white. Reading through this it seems like I assumed the green was ground (like literally every other electrical project I've done). Gonna go back out to the trailer storage tomorrow armed with my multi meter and hopefully solve this.
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05-27-2020, 03:07 AM #7
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05-27-2020, 05:08 AM #8
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The easiest way to solve this is with a meter that will read DC voltage. When you get to your trailer and get setup and ready to go, put you meter on the DC voltage scale that is applicable (your obviously looking for 12VDC. Connect the black lead of your meter to the trailer ground....the frame or some metal part that you know will be grounded. Then turn on the parking lights on your truck (make sure that the truck is hooked up to the trailer using the 7 pin connector that give you your taillights, turn signals, brake lights, etc. With the taillights turned on, stick the Red probe for the meter on each one of the wires until you find the one that is giving you 12VDC. Go ahead and check all of them, but now you know which one is the +12V. Finding the other wire is fairly simple also. Go ahead and turn your truck's lights off and then change your meter scale to check for ohms....or resistance. Leave the black lead connected to the trailer frame, and with the meter on the ohms setting, touch the other three wires (you already know which of the wires is the hot wire, so no need to test that one). At least one of them should show almost ZERO ohms between it and ground.
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05-27-2020, 09:03 AM #9
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Wow. Thanks for the reply. My first attempt I was basically doing this, but the tool I was using apparently wasn't up for the task. I use it around the house to see if the line is hot or not and it works great for that but didn't detect anything when I had the lights on for the trailer. I do have a nice multi meter. Electrical is my weak spot. I'm just competent enough to do the simple things around the house like wiring light fixtures, outlets, switches, etc. Beyond that I struggle and seek out help. Thanks again.
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05-27-2020, 09:05 AM #10
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Channging Battery Type?
Today, 07:27 AM in Electrical System and Wiring