Diodes and resistors

[blacklav]

Hi all, I`m in the middle of rebuilding a 1977 model D. Now the wiring is a bit of a mystery. There are components on the bike that do not appear to be used like the light checker, reserve lighting unit, Diode,resistor and the brake lining switch. The question is do I need a diode and resistor, as the electrics seem to work ok without them.
According to the wiring diagram. The diode is connected between the brake lining light and the starter button/switch.
The resistor is between the flasher switch and the main headlight.
Now I know a diode only lets current through in one direction and a resistor reduces that current/voltage, but why are they needed here?
What is their purpose?
Any info to shine a light on this problem much appreciated.

chris r

 

[XSLeo]

The diode is so when the rear brake shoes wear to a certain point the switch turns on the light on the dash on.
As far as I know there is no resistor between the turns and headlight, two totally separate circuits.
Yes the diode can be left out. I can't really see a need for the brake lining warning light. You should be checking your brake shoe wear every time you have the rear wheel off, you'll go through more tires than you will brakes.
Leo

 

[blacklav]

Thanks for the info Leo, so if I remove the light checker and reserve lighting unit, all should work ok. I don't know if these work anyway its just a big jumble of wires. There is so many in the headlight shell that its hard to close.
Thanks again
chris r

 

[Grinder]

The resistor you speak of is part of the reserve lighting unit. It would lower the brightness of the high beam when the low beam burns out.

 

[blacklav]

thanks for that Grinder.
So if I don't have a reserve lighting unit then I don't need the resistor yes?

chris r

 

[retiredgentleman]

thanks for that Grinder.
So if I don't have a reserve lighting unit then I don't need the resistor yes?

chris r

Correct.................if the RLU is gone then no need for the resistor.

If you remove the RLU, you would need to connect the blue to the blue/yellow at the RLU.

If you remove the resistor, you need to connect the yellow/blue to the yellow at the resistor.