The Bullet Board

The June 1999 to 2009 Bullet 350 and 500 bikes sent to the USA were fitted with a 4-wire alternator. Prior to that they were fitted with a 3-wire alternator. On the 3 wire alternator, the electric generated at the alternator was sent to the rectifier/regulator where the current was changed from AC to DC and then sent to the battery and lights.
That changed with the new 4-wire alternator fitted to the post June 1999 bullet models. Please see wiring diagram below. On that diagram you will see the alternator has one yellow wire, one amber wire, and 2 violet wires. If you follow the violet wires you will see they connect to the rectifier where the AC current is changed to DC current, then sent to the regulator to limit the DC voltage to 15 volts, then the DC current is sent to the battery through the black and yellow-red wires.
If you look at the other two wires on the alternator (yellow and amber) you will see they do not go to a rectifier but rather continue to be AC current. The amber wire is connected to an AC regulator to limit the AC current to 15 volts (remember it is still AC). The amber wire then attached to the headlight bulb suppling AC current.
So, to make a long story short, LED bulbs operate on DC current not AC current. If the subject LED conversion does not have an internal rectifier in the bulb housing, the LED will immediately burn up like a firework when AC current is applied.
So, the question is : does the subject LED conversion assembly have an internal rectifier which will convert the incoming AC current to DC?

Is there a wire diagram with the bulb?

Glad I didn't see this before buying my H4 LED headlight bulb. 2012 C5 and the bulb works fine. I don't remember anything in the documentation that mentioned AC.

Well cinders and ashes! The internal RR unit is not listed on the spec sheet so I am going with no, it doesn't. I can't see the diagram from my phone, but I know bikes in that range have an RR unit just for the headlight, where does that come into play?

DanFromVegas wrote: ↑Thu Feb 27, 2020 6:52 pm Glad I didn't see this before buying my H4 LED headlight bulb. 2012 C5 and the bulb works fine. I don't remember anything in the documentation that mentioned AC.

Dan I feel like I'm two steps behind you. One day I'll have something you want when you want it

The 1999-2009 Bullets had the 4 wire alternator, and the yellow and amber wire were not rectified, however, they did have a small AC voltage regulator. I am not certain what the UCE or 650 engines used. Does the LED spec sheet have any kind of internal wiring diagram?

The old Yahoo site had a bunch of wiring diagrams that could have been used to figure out which model year headlights are AC and which are DC.
I will see if I have any of those old Yahoo files stored on my computer, if so, I will post.
The Snidal Manual may have the wire diagrams also.

Here is a diagram provided by Kevin M for the EFI cycles 2014 I believe. He describes this as a 2014 B5 model. This diagram shows a three-wire alternator with the three wires going to the Rectifier/regulator. So, it makes sense that his LED conversion would work on the EFI B5 bikes.

Here is a diagram from Sihng for a 2011 C5. Again, a three wire alternator/magneto that goes through the rectifier/regulator.

Ok, last one, the 650 interceptor also uses a three wire alternator/magneto which all go to rectifier/regulator. So this LED should work on those bikes as well.

I am not disputing the wiring diagram but I am scratching my head. I can't get past this fact. I know for certain all Royal Enfield models shipped from the factory with a Wagner 4467 sealed beam from the early 2000's to when I left in 2016. If there is a transition from DC to AC somewhere how/why didn't the bulb change?

An old time Thomas Edison incandescent bulb (like the Wagner 4467 Bulb) will operate on either DC or AC current, the filament is just tungsten wire. The tungsten wire does not care about the direction of electric current so it can use alternating current or direct current. The Wagner 4467 halogen bulb has halogen gas surround a tungsten filament. Since it still has a filament, it will operate on either AC or DC.

An LED on the other hand is a Diode which means it has a positive and a negative pole or wires. It allows electrical current to flow in one direction only, if the current is reversed it will immediately (fraction of second) overheat and burn out.

So, there needs to be an internal rectifier in the LED bulb to assure that the electric current is flowing in the proper direction, (if AC current is used).

On the LED bulb in question ,I notice "Saucer shape" component below the LED . It is possible there is a rectifier or other electronics in that saucer that make the correct polarity for the LED. That is why it would be good to see the internal wire diagram for the LED bulb to see what is in there.