Headache and the brown wire mystery

[exvalvesetdabbler]

I have been trying to figure out how to have the front position light on without lighting up the tail light and gages after fitting a LED bulb.  Kind of stumped at the moment  thought I would test things before diving in. For some reason the front position light only comes on when the ignition is on and the headlight switch is in the first position. If I turn the key to the park position, only the tail light comes on. Aside from TL1(Bn) and TL2(Bn/W) wires crossed over in the headlight shell I have no ideas. Need to check when its dark if the instruments light up in park. I remember the front parking light working in the past but probably a long time ago and distant memory. The only wiring that has been poked recently is the horn terminals and the wires that run out to the tail light under the mudguard.

I have studied the wiring schematic and traced the brown wire, there are four terminations, front position light, tail light and two wires on the main switch PA and TL2.  So power on either brown wire at the switch should light up both lamps. I can't figure out why one lamp can get power and not the other one since there is a continuous connection between them.

I unwrapped an old wiring harness to verify the connection and the 4 brown wires are soldered together in the loom as they should be.

I'm not in any hurry to unravel the spaghetti in the headlamp shell and would welcome any insights before I dive further in.  The next move at the moment is to remove the battery and replace it with a bench power supply with current limiting before poking around. Probably early next week if time permits.

Having the position light permanently on isn't or shouldn't be that difficult, just need a diode in the existing brown wire feed to the bulb and then introduce a fused & switched power feed down stream of the diode.

Regards
Dave

 

[Johnwebley]

Can I suggest you fit an stop/tail LED bulb,

And ride with it on,
Being LED to consumption is negligible

Save a lot of bother

Sent from my SM-A546E using Tapatalk

[exvalvesetdabbler]

Thought about that, finding one that has the right approvals is not so easy. Would also need to swap out the guage lights, but some say that the heat from those minimises condensation build up inside.  16W  between them, that's more than my soldering iron!

Still need to get the parking light working which is turning out to be the hard bit for now.

Thanks
Dave

[Bryanj]

Honda designed so the front and rear parking lights come on together, only way to stop rear comming on would be to fit an extra switch to turn it off and that poses all sorts of problems if you forget to turn it on

[exvalvesetdabbler]

Yes, hence the diode to feed the front from switched live.  The light switch  and park would still  feed everything as it did before as should the park setting.

Dave

[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]

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.

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

[exvalvesetdabbler]

The ball ache is figuring out why the front bulb isn't behaving according to the schematics before I dive in and add the extra bits.

Regards
Dave

[exvalvesetdabbler]

Oops. The plilot bulb is plugged into Bn/W so explains what I have been seeing. Just need to dig out the plain brown wire socket now.  Must have been like that since about the late 90s when I fitted the new headlight shell and switchgear.

Something that's not tested on the MOT so not something I would regularly test since everything worked as it should with the ignition on and lights switched on.

Been a bit distracted  and stressing sorting out the MOT on my 4 wheel money puddle but this was buzzing around in my head and couldn't resist having a quick peek.



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Regards
Dave

[exvalvesetdabbler]

Finally got around to building a prototype adapter for a daylight running light.

It's probably over engineered and the plan is to miniaturise it using a PCB and surface mount components then pot it.

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Ideally a polyfuse will be included. One thing that has become clear is that there is no fuse in the circuit when the ignition switch is in park with the OEM wiring. In
Park the brown wire goes to batt.  With ignition and lights on the brown is fed from the 7A tail light fuse.

If the next person that comes along doesn't like it they can simply unplug it and plug the position light wire back in to the brown wire feed.
Regards
Dave

[Bryanj]

Yes there is, the main 15a is in the power line to the switch

[exvalvesetdabbler]

Ok, just put my other glasses on.  Having the switch connection labelled Batt and seeing how the other 2 fuses were fed from the switch I assumed the worst.  Non the less, it's still a bit of an odd setup having 7A protection when running and 15A protection when parked.  Probably saved  Mr Honda the cost of a 4 way fuse holder and a couple of meters of wire.

I am probably being over cautious wanting to fuse it down a bit with not knowing the failure modes of led  bulbs with inbuilt current drive chips.  A filament bulb when it pops can sometimes have a surge and sputter the remains of the filament inside the glass but the event is short lived an results in open circuit. With electronic components they sometimes just go into meltdown and not necessarily fail open circuit. With 15A protection they could make a bit of a mess before they burned up. This is why a lot of electronic devices have a non resettable thermal fuse or a resettable poly fuse embedded.

Regards
Dave