Headlight blew when I turn heated grips on

[Bones]

It doesn't happen every time but it did last night as I was leaving work. Bike was ticking over nicely as put lid and gloves on, swung my leg over, flicked the heated bar swith and the lights went out . Fortunately main beam was fine, so I engaged the 'fat bird on the back' light adjustment lever so as not to dazzle everyone and rode home. Anyone else had this happen?

 

[wildbeeste]

Nope but then I have the 1150 which has optimum power rather than the 1200

 

[Bones]

I did think it could be the CANBUS getting it's knickers in a twist and sending the current intended for the grips to the dip bulb. 'kin fangled systems. It is the first time it has happened and I'm sure it will be fine when I fit a new bulb tomorrow. Mind you, I'll make sure that I try the heated grips before setting off from home in case the bulb goes again.

 

[Pukmeister]

I think it is just coincidence.

You can't squeeze more amps into the lamp, it will only draw the amps it needs. The current flow is due to the load placed on the circuit, not the other way around. The headlight and heated grips are on two seperate circuits.

There may have been a slight overall voltage drop across the bikes wiring the instant you turned on the heated grips, due to the resistance of the heating elements, but I doubt this would cause an otherwise healthy lamp filament to burn out.

 

[GSmonkey]

My guess is this: your headlight bulb was on it's last legs. Switching on the heated grips would impose a voltage transient onto the system, enough to blow the (weak) filament. The heated grips are effectively a nice big coil of wire, which make a nice inductor - so when you switch on you get an inrush current (and hence voltage transients).

The canbus cannot force current anywhere, it can only open and close electronic switches. The current that finally flows to the device is purely a result of the voltage and resistance.

 

[Bones]

Thank guys for the useful info above, you know more about electronics than me. As I said this has never happened before and I’m sure everything will be fine when the new bulb is fitted. Instinct tells me that the bulb blowing was not pure coincidence though as the bike had been warming for a minute or two (obviously with headlight illuminating the surroundings) and when I sat on the bike the bulb went the instant I switched the grips on. I like the solution of weak filament that was about to blow anyway as this would mean the problem will not reoccur when a new bulb is fitted. It’s typical these things happen when you are about to set off on a 40 mile ride home in the dark, so it was useful to discover that full beam with the ‘heavy load’ switch (behind the headlamp assembly) flicked will lower so as not to infuriate other road users.

Thanks again for your collective wisdom

 

[PhilBolton]

Put it down to coincidence - put a new lamp in - and forget about it.

Phil

 

[Pukmeister]

A quick tip based upon experience.

The lamp element is the same in the dipped and main beam units, it's just the design of the lamp focus and reflector that causes the difference in beams. If you find your dipped lamp blows and only the main beam remains, you can find a safe place to pull over and swap over the lamp elements to give you dipped but no main beam as a get you home measure without dazzling oncoming traffic.

Of course, the best solution is to find a 24 hour petrol station with lamps for sale and do a lamp change on a nice dry sheltered forecourt.

As with all halogen lamps, avoid touching the glass with your bare fingers and handle by the metal only. Obviously let the hot lamp cool down before trying to remove and swap it.