Replacing taillight bulbs opposite ground LED

[Vazlov1949]

Working on my 49 Pilothouse. With the stock single taillight it was pretty hard to see my truck at night from the rear so I changed to an LED bulb that works great on the stock 6 volt system. It did need to be wired with the opposite ground to make it work. Is this going to be an issue in any way? I have tested my other lights but I have not started the truck since this change. Anything to worry about?

[Allen I.]

I think the only thing that is polarity sensitive is the charging system, but my knowledge of electric systems may not be worth the paper you print this thread on.

[Jerry Roberts]

Vazloz , Are you saying that your tail lights are now negative ground and the rest of your truck is still positive ground ? If so , I would not start the truck either .

[grey beard]

If you reversed your battery polarity, you may have already fried your voltage regulator. Reversing battery terminals is a big No-No! Take it off right now!

There is really no need to mess with all this. Just go to <superbrightled.com> and buy your bulbs there - only about twenty bukkz each, they fit into the stock tail lamp sockets. and they are NOT polarity sensitive - don't care how your battery is hooked up.

One word of caution that I had to learn the hard way. For Pilothouse tail lights that have the red lenses, youi cannot use white LED"s. Don't ask me why, but they show up very dim through the lenses. You must get red LED's to use with red lenses - much brighter. I know, cause I still have two extra white led bulbs laying around here somewhere. Go figure . . . . . .

Also, did you all know that the tail lamp lenses with the DODGE script are darker glass than most of the glass tail light lenses that fit our lamps? Well, they are! Any bulb will show up less bright behind these things, and here we are with 6-volt light bulbs. Even the LED's show up dimmer behind these things. Baaaahh, humbugggggggggggggg

[Vazlov1949]

Thanks for the advise. I did NOT however reverse battery cables on my battery at any time. I merely hooked up the wires coming out of the back of the LED opposite of what their colors would suggest. It would not work the other way. And I do have the red LED lamp so my single "Dodge " light is very bright. I was mostly wondering if there is a problem hooking up the black and red wire to ground and the white wire to power. I should know whether my truck is positive or negative ground but I do not. What is it? Thanks

[Merle Coggins]

Since your truck IS still positive ground, you did the right thing. Your truck is 'reverse' polarity acording to a modern vehicle, so you would have to reverse the wires for the LED lights. You shouldn't have any problems. Start 'er up and go.

Merle

[Vazlov1949]

Thanks Merle

I was up half the night researching various angles on this. I am encouraged by what you say. I couldn't for the life of me figure out why the direction of flow through one LED lamp would matter. I hadn't altered anything. I didn't wire anything backwards to the battery. I used the existing wires to my taillight. I just used a test light and the LED to determine how to make the LED light. I bought these LEDs from Harrison Specialties. They are not the screw in type with little tabs for the socket. They come with wires. I glued the lamp into the socket with "GOOP" auto cement. (not the hand cleaner) So much is said about the polarity of LEDs. I wonder if they really all will work with either polarity as long as you reverse the wires. I know you can't do this with the socket replacement type of lamp. I got tired of messing with the socket plug-in thingy with the little spring. I also wonder if they are all 6 volt compatible. I read something saying they only use 2 to 5 volts anyway. All I really know is that my single taillight is finally visible from more than 2 feet away. I will let the forum know if my truck blows up when I start it.

[billwillard]

The bulb is polarity senitive. If it doesn't work the way you install it just reverse the two wires which is reversing the polarity. Will NOT efect anything else so jump in and enjoy your ride.

[Vazlov1949]

Thanks everybody.

Steve

[Merle Coggins]

Yes, a LED (Light Emmiting Diode) by definition is a diode, and so it will only allow current to pass in one direction. I'm not sure how SuperBrightLEDs got around the polarity issue unless they have some type of rectification circuitry that allows it work in either direction. And a correct statement was made regarding the voltage requirement of a LED. However, the replacement LED's for 12 volt systems have reducing resistors to drop the voltage to the LED's. So if you used a LED lamp assembly that was made for 12 volts in a 6 volt system it may not work perfectly.

Bottom line... if you're happy with it, run it.

Merle

[TodFitch]

Yes, a LED (Light Emmiting Diode) by definition is a diode, and so it will only allow current to pass in one direction. I'm not sure how SuperBrightLEDs got around the polarity issue unless they have some type of rectification circuitry that allows it work in either direction. And a correct statement was made regarding the voltage requirement of a LED. However, the replacement LED's for 12 volt systems have reducing resistors to drop the voltage to the LED's. So if you used a LED lamp assembly that was made for 12 volts in a 6 volt system it may not work perfectly.

Bottom line... if you're happy with it, run it.

Merle

I agree with Merle's "bottom line".

But I did a little looking and it seems that many of the high power LEDs have a maximum reverse voltage around 5v. So just hooked on to a battery the wrong way could damage them.

But they are also very current sensitive so usually there is a circuit in the package that does voltage/current regulation. And many of the designs for those circuits are good for input voltages ranging from around 5v up to maybe 20v. Lots of products out there so the numbers will vary a lot. But there is a reasonable chance that a "12v" LED will actually work just perfectly in a 6v system.