Diode?????

[mack]

Can anyone tell me what the purpose of this is and what impact it has on the system when one fries! Got a sick puppy here and they hard wired the head light to fuse block to bypass the diode I think. Other than the black lead out of the relay, I can't see a relationship to the head light. WTF? 3 Phase ?

[MPittma100]

Diode

Mack,

This is from a previous post from Crazy Steve concerning the diode. May help you:

Things to check: diode going to the headlight relay, the relay, left handlebar control connections, high-low switch, headlight ground.

Try bypassing the headlight relay first (it's under the tank, above/forward of the coils). Unplug the relay, check for power on the red/yellow wire, if present then jumper the red/yellow and blue/black wires together. If the light now works, then either the relay is bad or the diode has failed. The diode will be located in the white wire coming to the relay from the alternator; trace it back until you find it (it will covered with a bit of vinyl) and check that.

It's usually one or the other of these. If not, you'll need to check for continuity from the relay through the handlebar controls and on to the light.

[ViperRon]

The diode is a rinki dinky way of eliminating one half of the sign wave from the alternator thus giving only positive pulses that go to the head light relay. Basically all that gets threw the diode is positive pulses and when those pulses get to a consistent frequency and amplitude it triggers the headlamp relay which establishes a self hold path and turns on the headlight.

So the thought process is that the starter will not turn over the bike fast enough to get that level of voltage but when the engine fires there is enough speed and amplitude. Actually its about the cheapest way to have a circuit trigger the headlight after start.


You can get a diode from radio shack I do not know the value of the original but to be safe when I got mine I got one rated for 50 volts because the max output from the alternator is 25 positive 25 negative sign wave. The current capacity is not important because the power draw is very minimal.

[mack]

Thanx

I'll do Steves check but thanx Ron. I hate just following steps without understanding why. This bike isa complete unknown with no history. Trying to backtarck the PO doings to determine problems is daunting but I know I am a member of the right site to, "getter done".

[3Phase]

Sorry, Mack, my hands are killing me after playing in solvents all day and it hurts to type. Tomorrow!

.