Question, which part of a typical automotive light bulb is the positive end and which is the negative? I ask because it would seem to me that there is something wrong with this picture:
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Question, which part of a typical automotive light bulb is the positive end and which is the negative? I ask because it would seem to me that there is something wrong with this picture:
Attachment 263996
The bottom end is usually the positive end and the outside the negative. Same goes for cigarette lighter plug
I guess I should clarify. I said automotive, but this is actually on a trailer. Typical 12 volt system is what I meant. But if I'm not mistaken, it's all the same polarity even on typical household light bulbs as well.
OK then, I'm not crazy. Why does the light bulb bottom (right side in this picture) have that screw going through the metal in the fixture (supposedly the positive side), and then it's screwed into the metal of the trailer.Quote:
Originally Posted by pineplace
Seems like they are grounding the positive side to the trailer, but in actuality the fixture is wired backwards. And that's why my replacement LED light bulbs won't work. The fixture, by design, seems to be wired backwards. What the heck is with that!
On dc circuits electricity flows from negative to positive. If the grounding screw was on the other side it would create a short and you wouldn't get any flow through the bulb.
Most of the time on a trailer the brown wire is the hot to all the lights, green wire is to right turn and yellow is left turn, white is ground maybe the screw on the right has an insulator and is just screwed to rail to hold light on. might start there. :twocents good luck
While your trailer frame is the negative side of the circuit and the positive comes in on the wire in actuality if the bulb holder is wired properly it does not matter which way the DC current flows through the bulb. If the positive voltage coming in on the wire goes to the case of the bulb, and the negative connection is the end of the bulb it will still illuminate, as they are not polarity sensitive. However on your LED lights the positive must be connected to the proper terminal as LEDs are polarity sensitive. If you are trying to use the LED replacement bulbs which look similar to the incandescent bulbs they will NOT work in the pictured fixture.
I'm not an electrician, but a retired Electronics Technician and a life long electronics enthusiast. Amateur Radio (Ham) call-sign = W5CPT -
Like Clint said, you can't wire an incandescent bulb backwards. It was done this way for an easier installation during assembly. Looks like yours actually has a ground wire in addition to the screw, which means you can install a fixture with a pigtail plug and LED light.
Yep, agreed, can't wire incandescent wrong, but still, the stupid fixture grounds the right side to the frame, so this fixture will not work for LED, because they designed it backwards. The engineer should be fired. Just sayin'
I am simply gonna use incandescent bulbs where they are screwed to the frame. At least I can use the LEDs in the 5 light positions at the top front of the trailer where they are screwed into fiberglass. I just flipped the wires and it works fine there.
Bet it reads "made in China" somewhere or maybe ACME.:Rofl
https://twistedsifter.files.wordpres...ts-catalog.jpg
https://tse3.mm.bing.net/th?id=OIP.5....1&H=220&W=160
There exists a proper code to do things, but we have become nation of blacksmiths.
Ed it looks like the wire are just pushed in from the back under the brass clips. If you remove it from the trailer you should be able to reverse the wires.
"gene"
It's not the matter of the wires, they are easy enough to swap. It's the screw that gets grounded into the frame of the trailer, and the fact that it goes through the plate which touches the bottom part of the bulb. It's supposed to be the "positive" but since it's screwed to the frame, it has to be the negative. LED replacement lights will not work in this configuration. The bottom of the bulb is supposed to be the positive (like every bulb ever made). The engineer that designed these fixtures musta missed a couple of key days of school.
You already have enough info to satisfy your question, so I won't beat that which is already dead. I will tell you how you can replace them for the last time, as I did on my boat trailer. Pitch all of them in the trash and go on line and buy sealed LED replacement lights. I had to do a little bit to make them last but they submerge, road grime and anything else I can throw at them and have no issues. In this case, cheaper to spend money. Happy trails. Or trailering, Or whatever.
Yeah I was gonna do that but I decided that since this will likely be this trailers last trip to IL I wasn't gonna spend anything else on it. It'll retire after this.
Instant fix - Take that screw out and put a nylon one in. Lowes or HD carries them.
I did not think of that, brilliant.Quote:
Originally Posted by Barnacle Bill
I'd have to buy a new trailer
That thing looks so old it was prob made before LED's existed.
If you insulate the screw, you will have to add a ground.
"gene"
A two conductor arrangement can become complicated. LEDs have complicated the world.
The continuning seemingly never ending hassel with boat trailer wiring was eliminated for me when I had LED lights installed with the trailer rewired with a third white ground wire run to each light so as to not use the trailer frame for return ground. Previously for me 99% of the time all my trailer light issues resulted from faulty ground wire and the screw into the trailer frame. That upgrade was done in 2009 and I haven't had any issues since. Knocking on some wood here hoping I don't have a trailer light issue the next time out. :yikes
Frame grounds do not work well over time. We have to learn this lesson over and over with our cars, our boats, and our aircraft and other moving objects such as trailers. Frame grounds were not used in the Apollo Project!
The goofy thing is, there are two wires running to every light. No real need for a ground, but they grounded the darn thing with the screw that holds it to the frame. And they grounded the wrong end of the bulb, therefore requiring backwards wiring, which is fine for an incandescent bulb, but not an LED. Replacing the screw with a nylon one like BB suggested is the perfect solution. Yeah of course simply replacing the fixtures with sealed LED ones is the ultimate way to go, but I'm too cheap. I already replaced the four big brake/running lights with sealed LED lights and they are great. I was simply trying to stick LED light bulbs in the remaining dozen marker lights when I ran into this reverse polarity issue.
Thanks for this thread. Didn't know that LED's were different.
I replaced the lights on a friends boat trailer recently because all of the fixtures were broken. Just bought a LED trailer light kit and while I was installing it I noticed there was a ground wire at each fixture in addition to the standard lighting wiring. If the extra ground wire was not grounded to the trailer that light would not work. To be a little more specific, the tail lights had the standard 1 yellow and one brown or one red and one brown but each had an additional white ground wire which leads to the question " how is your grounding"?
Not sure why a positive and a negative wire going to your light would not work unless grounded too. But a light bulb should definitely light up if it has a positive and negative wire with juice flowing. And in the case of LED lights, the juice has to flow the right way. All I can think of is, your other negative/ground wire is not connected good somewhere. Or since you mention it's brown, what I see on etrailer.com is that the brown wire is your running lights: https://www.etrailer.com/faq-4-5-way...eshooting.aspx If that's the case, that fixture would certainly require a ground connection (my trailer has separate white wire for negative/ground).Quote:
Originally Posted by crappie wrangler
A LED ( light emitting diode) A diode is really like a one way check valve....current will only flow in one direction through it.
One way, like some streets and some people. I say to some folks, "you diode". The message is most often missed.Quote:
Originally Posted by "G"
Attachment 264161
Now I understand evetrything!!!!!!
Are you sure ? :juggle
OK, that's simple enough but not simple enough for and even simpler mind. :dono
"gene"