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Headache and the brown wire mystery

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TrickyMicky:
Cannot work out why you don't want the rear light to come on. I have fitted LED bulbs to front and back, plus a couple of small LED's to the headlamp shell.  If you fit an LED in the rear, it MUST be a red bulb, if you fit a white LED the rear light will show as a pale pink. 

exvalvesetdabbler:
4 brown wired joined. The joint is in the harness close to where the bundle next to the horn that's supported by the rubber strap.

The decomposing adhesive on the harness is pretty revolting [ Guests cannot view attachments ]

exvalvesetdabbler:
Never appreciated there were so many 'rub joints' in a wiring harness.

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exvalvesetdabbler:

--- Quote from: TrickyMicky on July 01, 2025, 06:42:26 PM ---Cannot work out why you don't want the rear light to come on. I have fitted LED bulbs to front and back, plus a couple of small LED's to the headlamp shell.  If you fit an LED in the rear, it MUST be a red bulb, if you fit a white LED the rear light will show as a pale pink.

--- End quote ---

It's the guage lights as well. The filament bulbs are probably serving a useful function by minimizing condensation in gages so best to leave them as they are. Between the 4 bulbs they are pulling nearly 4x the current of the tail lamp. Seemed sensible to power the front position light from switched power independently and leave the whole lighting circuit untouched

exvalvesetdabbler:
This is the easy bit.

When on park front bulb is powered from the tail light circuit.  When the ignition is on  the front bulb draws power from the switched live.  The diode stops power feeding back and lighting up the tail light and gages.

With the lights on when running , power could come from the brown wire or the switched live, most likely the switched live because it will be 0.2v higher than the lighting  circuit if using a Schottky diode.

On park the bulb will get 0.2v less which shouldn't be noticeable since most half decent led bulbs have a constant current drive chip embedded.

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Regards
Dave

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