LED bulbs and electrical issues

[T250tut]

Hi All
1977 XS650D UK spec
Wiring is fine and all works OK - not sure if ignition switch is original as I can use position 2 on the ignition OR the on off on the right hand switch to work the lights
BUT
when i use an LED bulb in the rear T/L it glows faintly with ignition on / lights off - it does work correctly when the light are switched on as both tail light and break light.
all the dash warning lights / systems are working properly and no faults are triggered

I have an LED H4 headlight bulb in the front as I have on all my other bikes circa 1970's and I have not had this issue before so whats different with the XS???

Used bulbs from these guys in everything else and cant recommend them highly enough for the improvement they make to 60's & 70's Japanese 2 strokes
https://www.dynamoregulatorconversions.com/the-cdrc-online-shop.php
Cheers

 

[Downeaster]

Sounds like there's a little current still flowing with the light switch off. It wouldn't bother me but if you place a small resistor on either lead of the LED it should go away.

It'll take a little experimentation to get the resistance right so the light is off when the switch is off, but still at or near full brightness with the switch on.

I wouldn't do anything permanent until I tried it tho, I'm not 100% sure it will work.

 

[zrx1100]

remove or bypass the reserve lighting unit for an H4 retrofit to function properly. it is drawing too little power so the unit is sending current to the high beam

 

[zrx1100]

https://www.xs650.com/threads/headlight-bake-off.68636/

 

[T250tut]

remove or bypass the reserve lighting unit for an H4 retrofit to function properly. it is drawing too little power so the unit is sending current to the high beam

Headlight works fine on main beam and dip - its the tail light that has issues

 

[Wagner73]

Headlight works fine on main beam and dip - its the tail light that has issues

As @zrx1100 has implied, in order for led's to be happy in an XS650 - and forgetting directional signals for now, as that's a whole different subject - you need to eliminate the light checker (which may be more of the problem in this case) AND the reserve lighting unit. The light checker you can just unplug; RLU elimination here:

http://www.excess650.co.uk/tips & tricks.htm

 

[T250tut]

I get that possibly the light checker doesn't like the lower resistance in the LED bulb and and that would triggers the circuit but that is designed to switch on the headlamp main beam - the headlight is not coming on
Also if it was the lower resistance triggering a back up system to switch the lights on surely the light would be at its intended brightness not a dull glow of approx 1/3 its brightness???

 

[zrx1100]

i monitored the voltage with the reserve unit and it was doing strange things and the voltage accross low beam was non-zero. just disconnect/bypass these items and try

 

[Wagner73]

I get that possibly the light checker doesn't like the lower resistance in the LED bulb and and that would triggers the circuit but that is designed to switch on the headlamp main beam - the headlight is not coming on
Also if it was the lower resistance triggering a back up system to switch the lights on surely the light would be at its intended brightness not a dull glow of approx 1/3 its brightness???

The light checker doesn't have anything to do with the headlamp, that's all the RLU. The light checker monitors the tail lamp...why don't you simply unplug it and see if that helps?

And as @zrx1100 has opined, I would bypass the RLU too and try it. Too many little trace current gremlins in these bikes that don't like the low current draw of LEDs.

 

[Its been a long time]

The light checker doesn't have anything to do with the headlamp, that's all the RLU. The light checker monitors the tail lamp...why don't you simply unplug it and see if that helps?

And as @zrx1100 has opined, I would bypass the RLU too and try it. Too many little trace current gremlins in these bikes that don't like the low current draw of LEDs.

Yes, agreed. Who knows what's going to happen mixing fifty year old electronics with modern day LEDs? I removed all the ancient electronics from my back from the dead 650D project as a matter of course.

 

[Wagner73]

@T250tut - Any joy here? We really appreciate feedback!

 

[650Skull]

Going iff the standard Euro diagram,Euro spec 77 doesn't have a RLU. They don't have the white headlight fail light on the dash.

Have a light checker.

 

[Wagner73]

Going iff the standard Euro diagram,Euro spec 77 doesn't have a RLU. They don't have the white headlight fail light on the dash.

Have a light checker.

Good info, thanks! So just unplug the Light Checker and the problem will likely go away. My Light Checker did not like to coexist with my LED taillight either (except maybe the Sylvania Zevo's which must draw a little more current than others)

And again, we love feedback!

 

[T250tut]

Tried unplugging all sorts of stuff - probably even the auto cancel :0) nothing worked so put an incandescent bulb back in and everything works as it should

 

[Wagner73]

Hmmm, weird. There must be something going on in the wiring or switchgear to feed back or leak such that the taillight will illuminate slightly when an LED is used.

On my US-spec 78E I have unplugged and removed the light checker, unplugged and jumpered per instructions the RLU, replaced every and ALL bulbs with LED's (plus an LED-compatible flasher unit), and all lighting functions perfectly.

One thing occurs to me...you said that with ignition on and light switch off, TL glows faintly. Well, unfortunately I don't have a 77 euro-spec wiring diagram in front of me, but the later (77 & up, not sure where it started) US bikes had the TL always on when the ignition was on...the switch just controlled the headlight and meter lights.

I'm sorry you're having these issues, and if I can think of anything else, I'll post it here. Maybe another member will have an idea.

Edit: Thought of something else...if your ignition switch has the "park" circuit, you could be getting a slight short between the "on" and "park" positions/contacts which might cause what you are seeing?

 

[zrx1100]

did you measure voltage accross the terminals of the bulb as you go through combination of ignition and brake applicaiton? you should see voltage being applied to the signal pin as you activate brake lever/pedal. take note of any leakage if present.

 

[AUTOMAN]

Just short the LED's with some 480 ohm 1/4 watt resistors.

 

[Wagner73]

Just short the LED's with some 480 ohm 1/4 watt resistors.

Seems a little bit of a hot, crude solution. Plus where to cobble up a connection?

Would be way better to find the root cause and fix it.