Headlight bulbs blowing and voltage higher at headlight than battery

Ahoy the forum. Bit of a peculiar one. I've been having headlight bulbs blow every so often, which I put down to vibration until I put an LED bulb in and had that fail too after a couple of months. That finally prompted me to check the voltage at the connector, and I saw 15.2V across the open circuit.

Not crazy high, but higher than I'd like, and at this point I assumed that the battery was seeing that voltage too. So I ordered up a £30 Chinesium reg/rec and have just thrown that in.

Now I'm seeing 15.0V at the headlight connector (open circuit). The plot thickens when I checked across the battery terminals and got a more reasonable 14.6V.

I've checked back and forth a few times and the voltage is consistently higher at the headlight than the battery, and both stay pretty much constant with revs. I don't see any sharp spikes or dips when revving, just the usual 0.1V or so brief wobbles before it settles down.

There's no aftermarket wiring or any modifications or electrical repairs or bodges to the bike (2011 F650GS twin).

I assume that this is some sort of evil canbus sorcery, but was wondering if anyone else has seen anything like it.

At this point I'm minded to just feed it a regular diet of cheap bulbs rather than spend time or money investigating further, as long as it's not cooking the battery.

40 yers ago, when I was into road rallying, I modified the electrics in the car so that I had 15.5v at the lamp terminals, but rest of car was at normal charging voltage.
As a consequence, at every event, my lamps were taken out and checked to see if they were illegal (they were not) yet by lights were so good I failed to get a good photo of the car at nights. Photographers set their cameras for normal exposure, and my lights always swamped them.
This is the bonus of high voltage at the lamp. Remember that light output goes up to the square of the voltage, so your lights are twice as bright as they should be. Downside is short lamp life.
Myke

Oh, they're nice and bright, briefly. I'm wondering if this is normal for the midi-GSes though. I've had it for 7 years and it went the first few without eating bulbs at this rate.

Not a huge drama as bikes go, more curiosity.

My F650GS and Recent F700GS both blow front headlight bulbs. Probably every 2000 mile or so. The tail lights are led and the indicators whilst filament are not on all of the time.

I just put it down to heat and age, never checked the votages and never observed any brightness or dim whilst revving the engine.

Definitely not CANbus since that is a Controller Area Network that facilitates communications amongst various control modules. The ZFE module controls chassis electrics. AFAIK there is no way for the ZFE to increase voltage though. The ZFE uses solid state relays to switch electrical circuits.

Wheres Ash when you need him??
Of little use to you, but I had a 2009 for several years without any prob, I think I replaced one in three years?

Buy two mini type relays and "feed" them from the battery and use the headlamp wires to trip the relays

relatively cheap fix and a more stable voltage

You could also search E bay for a seller called Gammotronix who sell a small in obtrusive Voltage monitor that you could link into the light feed and see if you are getting voltage spikes while riding ?

Bem said:

Wheres Ash when you need him??
Of little use to you, but I had a 2009 for several years without any prob, I think I replaced one in three years?

Click to expand...

You rang...

Never had any bulb problems with my numerous F series of bikes..



I do run Cyclops LED bulbs in my headlight now ( simply stunning, but costly )

https://r.search.yahoo.com/_ylt=Awr...ht-bulb//RK=2/RS=wEQ3UW6e6Qrcn2hI_RvL01tknUs-

It could be a poor earth connection on the rectifier,
The output voltage can run high as the voltage regulator dumps the excess to earth/ground,
The generator is running max output As its permanent magnets, unlike cars and older boxers,
The battery is buffering the excess so may read slightly lower,
also a sulphated battery can cause issues as its not absorbing current so voltage rises,