What Voltage is your Trailer At?

[zabooda]

Check your voltage from the ground where you are reading 7.5 volts to the actual ground (truck chassis). Sounds like a floating grounding. It should be in your connector. If you have 12 volt on the hot then your probably have 4.5 volts on the negative which means you have no negative to ground but is back fed through the ground to another part of the ground circuit which is usually lights but not with LEDS so perhaps the backup device or license plate bulb. Bottom line: no solid ground to the vehicle.

[rsinger]

I think you need to sell the boat and trailer. Give me a call, I'm sure we can work something out.....

wtf, everything's new. I go with the floating ground issue. I got burned by that a couple of years ago. My meter ground connection just wasn't making a 100% connection to the trailer ground connection.

[mmandley]

It could be a floating ground but i am checking the + AND - of the wires going to the lights. Only reason i can think of a floating ground is if the trailer is actually grounding through the hitch on the truck.

I had the lights pluged into the truck but not the hitch

[rsinger]

It could be a floating ground but i am checking the + AND - of the wires going to the lights. Only reason i can think of a floating ground is if the trailer is actually grounding through the hitch on the truck.

I had the lights pluged into the truck but not the hitch

Someone can correct me if I'm wrong, but I think one of the connector leads pushes the ground through to the trailer. Then on the trailer end that same lead will eventually connect to the trailer frame, which is used as ground and one terminal of each light fixture connects there. So even with the hitch not connected the appropriate voltages should be found on the trailer.

[parrothd]

Did you install the LEDs? Did you install them in series instead of parralle?

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[rca]

You have any idea what gauge wire is used for the trailer wiring? Do they wire each light in series or parallel. Most of those LED circuits are probably constant voltage or constant current setups. I'm not sure what is most common in trailer wiring. You know that the wire acts as a resistor, so you can get pretty significant voltage drop over long distances for thinner wire.

[mmandley]

@MLA I used the trailer as a ground, and the wire ground, both read the same at each point. The meter readings where consistent any place i checked.

@parrothd I have been working on the LEDs i want to install. All the testing i wrote up today was how my trailer came optioned. I Should have measured the trailer before i touched it but i didn't. The last post is only the factory trailer wiring. Nothing has been changed or added as of this point. Trailer is a paralleled system + to + and - to -. LEDs only work in 1 direction, if you try to hook any of them up with + to - they just don't work.

@rca its the factory harness which i believe is 16 or 18

[MLA]

@MLA I used the trailer as a ground, and the wire ground, both read the same at each point. The meter readings where consistent any place i checked.

@parrothd I have been working on the LEDs i want to install. All the testing i wrote up today was how my trailer came optioned. I Should have measured the trailer before i touched it but i didn't. The last post is only the factory trailer wiring. Nothing has been changed or added as of this point. Trailer is a paralleled system + to + and - to -. LEDs only work in 1 direction, if you try to hook any of them up with + to - they just don't work.

@rca its the factory harness which i believe is 16 or 18

I would go back to the point where you 1st recorded the low voltage and measure again, but this time, place the meter's ground lead on a ground point on the truck instead of the trailer.

[EarmarkMarine]

Think in terms of the length of the vehicle plus the length of the trailer plus the round about path. Double that for the collective B+ and ground. Then measure the current consumption with all trailer lights active. Consider the wire gauge along the way, which might also be inconsistent. Coinsider all the connections. Crimps can be serious sources of resistance. Again, with this data a substantial voltage drop doesn't surprise me. The higher the current draw (with all lights plus a few additions) will expose the limitations of both wire gauge and connection quality. A bad connection may not show up using the minimal current used in a multimeter to check resistance. Problems are exposed with a higher current draw and especially measuring voltage when the circuit is loaded. Measuring the voltage drop is the most effective method. You just have to use a little logic to narrow down the specific cause or location. It's very simple if we don't complicate it.

David

[rsinger]

It's very simple if we don't complicate it.

David

You kidding? We're 3 pages deep on this thread. I think we've complicated this, and a half.

You are right though. Stuff like this always ends being something simple.