Can an LED bulb be used with Commando positive ground

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Yellow_Cad

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I picked up an 1157 LED bulb to use in the taillight of my 73 Interstate. It doesn't do anything. Is this because of the positive ground? I did put the same bulb in a Triumph car (TR6) with negative ground and they work fine.
 
No, an incandescent bulb doesn't care which way the current flows. Check your ground connection. I assume you don't have tail or brake light with the bulb, so it is unlikely it is a problem with both feeds, but if the ground isn't faulty then that's the next step.
 
LEDs are polarity sensitive. Most require a negative ground. Will not work with a positive ground. In fact, check it in your Triumph again to see if it still works. If you isolate the tailight socket from ground on your Norton you can hook up seperate wires pos. to pos. neg. to neg. and the light will work. I prefer to change over to negative ground on the Norton. If you do, the zener will not work and the electronic ignitions need to have the input lines swapped. If you are running a stock alternator with a halogen headlight just chuck the zener.
 
OOPs! I didn't read closely enough. LED's are certainly polarity sensitive. Disregard my previous post.
 
Is there a down side to converting my Commando to negative ground? What is the actual function of the zener? Right now, everything on my bike is stock (ignition, alternator, headlamp, etc.). I am considering a switch to electronic ignition, 3 phase, halogen headlamp and LED taillight and blinkers. What are the actual steps to convert from positive to negative ground or are there some good posts from the past on that?
 
Yellow_Cad said:
Is there a down side to converting my Commando to negative ground?
Click to expand...

You will need to buy some new parts, that's about it.





Yellow_Cad said:
What is the actual function of the zener?
Click to expand...

The Zener is the voltage regulator.



Yellow_Cad said:
Right now, everything on my bike is stock (ignition, alternator, headlamp, etc.). I am considering a switch to electronic ignition, 3 phase, halogen headlamp and LED taillight and blinkers. What are the actual steps to convert from positive to negative ground or are there some good posts from the past on that?
Click to expand...


It should be easy enough to do, but you will have to change the Zener and rectifier for negative ground items, or just buy a regulator/rectifier box (Podtronic) to replace them, as they can normally be wired to suit either polarity.

Any other polarity sensitive items like electronic ignition & coils will have to be wired negative ground.

If you fit LED blinkers then you will need a suitable neg ground LED flasher unit.
 
I've never done it, but I think you should be able to swap the output leads from the rectifier. As for the zener, if your charging system is not keeping up with the power usage I see no need for it. It's a crude form of regulator, sending current to ground when it's breakdown voltage is reached to keep the battery from overcharging. I think breakdown is around 13 volts. I know my stock charging system doesn't keep up with the halogen headlight, which I have hard wired ON, so I guess the battery will never overcharge.
 
JimC said:
I've never done it, but I think you should be able to swap the output leads from the rectifier.
Click to expand...

Not easily done with the Lucas stud rectifier as the stud is the ground, you'd need the negative ground version of that unit to replace the positive one, unless the stud (+) fixing was isolated from ground and was connected to the battery wire and the output (-) terminal then connected to ground?

With the small square encapsulated type replacement rectifiers there wouldn't be any problem, they would just require a switch of the + & - wires.
 
I didn't have have an actual rectifier in front of me when I posted before. I'd forgotten about the stud. I just hadn't thought it through. My apologies.
 
there might be some options at http://www.superbrightleds.com/cgi-...tion=DispPage&Page2Disp=/tail-brake-turn.html that would work. Some LED bulbs have a bridge rectifier inside and are not polarity sensitive, though don't know if that is the case with these...if not you might be able to open one up and reverse the internal wiring. They also sell bare BA15 bases and adapters to use other bulbs so that might be an option if the adapted bulb can be installed either way....anyway lots to look at on their page
 
Re:

JimC said:
I've never done it, but I think you should be able to swap the output leads from the rectifier. As for the zener, if your charging system is not keeping up with the power usage I see no need for it. It's a crude form of regulator, sending current to ground when it's breakdown voltage is reached to keep the battery from overcharging. I think breakdown is around 13 volts. I know my stock charging system doesn't keep up with the halogen headlight, which I have hard wired ON, so I guess the battery will never overcharge.
Click to expand...


True with the headlight always on but the stock Lucas system can boil the battery if the zener fails, have heard of a few cases....so probably best to retain it in case the headlight burns out and you don't realize right away, though one of the tricolor voltage indicators mentioned earlier would give a high voltage warning by flashing green. FWIW installed one on my bike and posted on it awhile back http://www.accessnorton.com/voltage-monitor-demo-video-t7576.html
 
Converting to neg ground from pos earth and retaining the Zenor diode would be a feat worth the bragging rights as its body mount is part of current path - must hang with some rubber of plastic involved. Most me included use after market reg/rectif like Tympanium or Podtronics or Radio Shack.

I'm chucking on a cartoon, people discussing modifications with the neg ground converter - who says - yes it was hard to keep it as original as possible down to the Zenor. If a factory 180 watt alternation, that'd be two Zenors and matched too.
 
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