Electrical failure

Hopefully,some of the more more learned members will be able to point me in the right direction with my electrical problem. 

With the horn, as per normal, connected and the ignition is turned on I blow  the fuse and lose the dash info, rear light and indicators which are all on the same circuit.  I have changed the horn but with the same effect.

** Note I do not have to press the horn button to cause this, merely turn the ignition on. 

Has anyone had a similar problem? I guess it is either the handle bar switch unit or a short in the wiring. Rather than chasing a short circuit in the wiring it would be helpful if someone had experienced a similar problem and could point me in the right direction. I would appreciate any help you can offer.

cheers

george

I've never had that one , but my horn stopped working once , and after a squirt of contact cleaner into the switch it started to work again .............so maybe the switch is sometimes prone to problems .

First up, I'll say that I've not had this problem. 

But I'm a bit confused from the description just what role the horn is playing in the problem, if any. Basically, if I'm understanding things right, you blow a fuse every time you turn the ignition on. What happens if you disconnect the horn and turn the ignition on - does it still blow a fuse?

Is this still the same problem you had back in 2016, all ok without the horn connected, but blows as soon as the horn is in circuit when ignition turned on, a 2010 Bandit ?

The horn wiring is pretty simple, there is 12v from the fuse on the orange/green wire all the time.  When the horn button is pressed an earth is applied on the black/blue wire.  

First thing I'd try is looking for the 12v on the O/G wire without the horn connected, then look for an earth when the horn button is pressed.  If you know how to use a mulitmeter or test light those two test should prove your bike wiring is okay.

From memory you've changed OEM horns a couple of times so it should not be the horns, you can test them by just connecting the two terminals across a battery.  I can't remember for certain but the two terminals should be isolated from the body so it doesn't matter which way round you connect.

My guess if all the tests prove to be ok is that when you connect up the horn there is a slight pulling on the O/G wire.  I reckon this wire has been rubbing on something and has worn the insulation through to the bare wires.  When the horn is not connected the wire is loose and is not touching the chassis, but when connected there is enough tension that it rubs.  

Bit of a guess as the symptoms are not normal, if you come over to Tassie in Dec I'll have a look at it for you  

barry_mcki wrote:

Bit of a guess as the symptoms are not normal, if you come over to Tassie in Dec I'll have a look at it for you  

Good work Barry, we need a couple more to try and make it a national meet

3 states represented isn't too bad but only 2 from the main land is a bit low

Thank you for the replies. 

Yes Barry it is the same problem. I put it in the to-do basket and forgot all about it as even when it was working no one, especially car drivers, could hear it.
The police, transport dept, politician and the media were all present for the last "lets get Mt Glorious bikers" blitz. The transport dept people were checking every bike for defects and there were a lot of bikes lined up in the car park. When it was time to check my horn there were so many bikes reving to check noise levels and horns being tested the examiner assumed one of the feeble beeps was from my horn. He was happy and sent me on my way. With the constant mass police presence on the mountain every day I know I am pushing my luck - so time to start investigating

cheers

george

Hopefully,the following test results may assist you in suggesting, the cause of the fault or further tests to be taken.


Wiring at: horn button – Black/blue & Black/white.           - Horn: Black/blue & orange/green


Test results


Ignition on: O/G at horn-  11.46v                at horn button – 0v         B/G  = earthed (continuity)


Ignition off:       
O/G  wire at horn to  frame          = earthed (continuity)
        = resistance settled at 2 ohms (after jumping around 22.4 to 0)


O/G to frame at horn button       = earthed an 1.4ohms  (meter set on 200)


Barry we have a friend in Hillier and were contemplating a holiday either in NZ or Tassie. If we make it to Tassie we will look you up for a coffee.

cheers


george

Can you place a test light on the two horn wires (without the horn in circuit) ?  It should only light when the horn is button is pressed (with ignition on).  

The wiring is very simple:



There is very little in the horn wiring, so to be blowing fuses the 12v on the O/G wire must be seeing a short to chassis.  I doubt it's anything to do with the horn switch,  it could be stuck permanently on and it would not cause a blown fuse.  

There's only two senarios that fit that I can think of, either the O/G wire has rubbed and is touching a bare earth (but only when the horn is plugged in), or the horn itself is presenting a dead short.

You would think by changing the horn it would cancel out the second scenario, but its possible you've got two defective horns.  However if they are not OEM horns and are manufactured with one connector wired to the horn body this could also be blowing fuses if wired a certain way.  A simple test to rule this out is to swap the two wires on the horn.  Have you tried placing the horn directly across a battery ?

As you suggested "A simple test to rule this out is to swap the two wires on the horn" fixed the problem. Things are very simple when someone points out the obvious - thank you Barry.

As an aid to someone who may this problem.

The original failure happened with an after market horn. When I replaced this horn with the OE horn the failure re-occurred. I did not think to check if the horn had to be connected in a specific way. After stripping the horn button switch and checking for damaged wires and cleaning all contacts I replaced the fuse, switched on the ignition and pop fuse gone. When further checking the wiring harness and connections I did not disconnect the wires at the horn so each time ignition on and pop.So I disconnected the horn and forgot about the problem.

When I re-connected the horn tonight. after Barry's suggestion. and turned on the ignition all OK and horn works. I did not try swapping the wires over to check if the failure re-occurred as I am going over the mountain tomorrow morning and have no spare fuses left. 

So I would appear if the two wires at the horn are crossed over then this may result in a blown fuse and you will lose power to the dash, brake lights etc.

cheers

george

An old and wise instructor once told me, look for whatever you last changed/worked on, the fault will usually be right there.  Well done tracking it down.

I don't remember my OEM horn being polarity conscious but it is something to be wary off.  
BTW placing it directly across the battery the wrong way round would have been hmm... enlightening