Flashers blowing fuses K100

[john11668]

When the courier delivered my bike   (85 K100) the flashers were working
Took it for a ride and they had stopped . Fuse blown
Fitted new fuse and got some strange behaviour, ( lights on continuous) but then settled down .
Took it for another spin and fuse blew again.

Have done a search  and there are lots of flasher issues but don't see many referring to blowing fuses.
I am hoping to resolve over the winter, (so have a bit of time I can spend .
What is the best (most methodical) way to work through the system to try and resolve this.

I suspect the previous owner may have been aware of this problem hence the bike was cheap(ish)
I suspect he would not know where to start with resolving .
Clearly I will do a visual to inspect for chafing wires etc  but after that  which parts are the likely culprits     

[Scott_]

Which fuse is blowing. The flasher unit is fed from 2 sources.
The flasher gets direct power from fuse #3, so the ign switch will have no effect on it.
The flasher unit also gets switched power from fuse #7 as well.
Fuse #3 wire Red/White(stripe) feeds the flasher unit as well as the power feed for the clock in the inst cluster.
Fuse #7 wire Green/Brown(stripe) feeds many items. Cooling Fan, Horn, Horn relay circuit, Alarm system(if equipped).

You may want to check the wires on the back of the hazard flasher dash switch, not uncommon for leads on the back of those switches to break, could cause a intermittent short circuit issue.

Though what I see of the switching circuits, the dash switch as well as the left/right turn signal switches, all 3 take the trigger lead from the flasher module and ground it to activate the flashing circuit. So I would think that any skinned wire/grounding of the leads would simply just turn the signals on as if you pressed the switch.

If you are blowing fuse #7, I'd check the cooling fan.

[john11668]

It is the fuse 3 which is blowing  . The clock goes off too.
Will check behind the hazard switch. maybe the transporter had one of his straps in that area!

[john11668]

It is the fuse 3 which is blowing  . The clock goes off too.
Will check behind the hazard switch. maybe the transporter had one of his straps in that area!

Can I just disconnect the Hazard switch to eliminate that . (It is after all an option in UK).
The bike has an auxiliary fan switch fitted. (Previous owners handiwork) I understand that the bikes own auto switch works but PO just liked to be able to switch on the fan a bit sooner. Wonder if anything there might affect it !

[Scott_]

It is the fuse 3 which is blowing  . The clock goes off too.
Will check behind the hazard switch. maybe the transporter had one of his straps in that area!

Can I just disconnect the Hazard switch to eliminate that . (It is after all an option in UK).
The bike has an auxiliary fan switch fitted. (Previous owners handiwork) I understand that the bikes own auto switch works but PO just liked to be able to switch on the fan a bit sooner. Wonder if anything there might affect it !

You could disconnect it. Follow the wire harness from the switch, there should be a 3 pin connector that you could disconnect, most likely under the fuel tank.

I would be curious of the PO's wiring of the fan switch, specifically how they wired it.........

[john11668]

You could disconnect it. Follow the wire harness from the switch, there should be a 3 pin connector that you could disconnect, most likely under the fuel tank.

I would be curious of the PO's wiring of the fan switch, specifically how they wired it.........

Will disconnect this weekend and see what transpires .
will also check out the fan switch too . Do you have reservations about it ?
Tank off should give me  a good chance to look for chafed wires too

[Scott_]

There can be many ways to wire in a manual switch to power the fan motor.

The factory design is to have the motronic controller provide a ground to the fan relay coil, that then(through the relay contacts) sends the +12v(from fuse #7) to the fan motor.

Many owners that have installed manual fan switches have preferred to wire one side of their switch to frame ground, and then wire the other side of the switch to the same motronic connection on the fan relay. That way either the manual switch or the motronic turns on the fan relay. This is how I have wired both of my bikes.

Another option would be to connect one side of the switch to a fused +12v source(hopefully the same fuse #7 circuit, if not then most anything could happen) and the connect the other side of the switch to the fan motor lead.  Unless you really know what you are doing with wiring, this method is less than ideal. Not that it won't work or can't work, but that it has the potential for other problems.

It is not uncommon for fan motors to seize up and/or go bad and blow fuses......

[john11668]

This is a bypass switch  which causes the fan relay to pull in.
I think he has wired it back to front though as it has a neon which comes on when the fan is off.

Could not find any chafed wires today but replaced the fuse and took it for a ride .
All was still working fine when I got back  so am thinking maybe I just had a duff fuse . Did work when first fitted though.
Will only see on a longer run!

[Scott_]

Just out of curiosity, what size fuses were there. They both(#3 and #7) should be 15A.

[john11668]

Just out of curiosity, what size fuses were there. They both(#3 and #7) should be 15A.

both were indeed 15A

[john11668]

Been out for a decent run and all seems to be holding up !
Wont worry unless it plays up again .

[john11668]

Just to follow up :-

I had to take the fairing off to secure a loose front flasher ( clearly had been knocked  off and not properly fixed!  It is now  secure )
One  flasher was connected with male and female insulated  bullet connectors.  One was connected with bare male and female spade connectors which were tucked behind the horns.
I think I may have found why fuses were blowing !!!!

Now have a different prob  so am off to instruments section.

[Laitch]

Thanks for the update, John. Good work.