Headlight comes on when using brakes

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estranged

Joined Aug 2009

168 Posts | 0+

Discussion Starter
• Oct 23, 2013

• #1

Hopefully someone on here can help as i'm getting annoyed with this new problem.
The bulb at the top/center of the headlight comes on when I use the brakes. Thought it was to do with an l.e.d. unit I had put on there, but it does it with the original rear light unit too.
If i disconnect the rear light unit altogether and use the brakes then the headlight bulb stays off.
I just can't figure this one out and it won't pass the mot like this and i've been bikeless since the beginning of July

 

Slackey

Joined May 2013

111 Posts | 0+

Tattershall

• Oct 23, 2013

• #2

Sounds like an earth fault on the brake lamp. This usually happens because people put single filament lamps with a single pole at the base in instead of a double pole double filament lamp, so when you press the brake the current passes through the side light circuit too.

 

E

estranged

Joined Aug 2009

168 Posts | 0+

Discussion Starter
• Oct 23, 2013

• #3

When you say pole do you mean the metal on the flat part on the bottom of the bulb?
It's got double filament bulbs, and if i'm thinking right on the poles, it has double poles as well.

 

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Andywhedd

Joined Jun 2013

87 Posts | 0+

Essex uk

• Oct 23, 2013

• #4

It's an earth fault some where for sure

 

Slackey

Joined May 2013

111 Posts | 0+

Tattershall

• Oct 23, 2013

• #5

Yep that's what I mean about the poles. In that case you have an earth fault on the rear light, you will not see it when the side lights are on because you would expect the front light to be on as well then.

 

E

estranged

Joined Aug 2009

168 Posts | 0+

Discussion Starter
• Oct 23, 2013

• #6

Great, i've got no idea on how to find out where the earthing fault might be.
Thanks for the info Mr Slackey and Mr Andy.

 

Slackey

Joined May 2013

111 Posts | 0+

Tattershall

• Oct 23, 2013

• #7

Where in the uk are you? If you are in lincolnshire area I will have a look for you if you can get to me (I am an electrical engineer)

 

E

estranged

Joined Aug 2009

168 Posts | 0+

Discussion Starter
• Oct 23, 2013

• #8

I'm in Dagenham, so a bit of a distance from you. Thanks for the offer though.

 

Slackey

Joined May 2013

111 Posts | 0+

Tattershall

• Oct 23, 2013

• #9

Ah yep bit of a trek lol

 

E

estranged

Joined Aug 2009

168 Posts | 0+

Discussion Starter
• Oct 25, 2013

• #10

Right. Fitted original rear light unit earlier. That's stopped the headlight coming on, but I have another problem.

Switch headlights on, both rear bulbs light up, apply brakes, one bulb goes off other one shines brighter, swap bulbs over and same bulb goes off/shines brighter.
Apply brakes with headlight off, both bulbs come on but one is brighter than the other, again swap bulbs over and same bulb is bright/dimmer.

Any ideas? Still a dodgy earth somewhere?

 

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Andywhedd

Joined Jun 2013

87 Posts | 0+

Essex uk

• Oct 25, 2013

• #11

Yeah sounds that way, I'm in wickford ss12 postcode also happy to lend a hand if you can get to me much closer

 

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Andywhedd

Joined Jun 2013

87 Posts | 0+

Essex uk

• Oct 25, 2013

• #12

Did you have to cut any wires etc when you put other unit on??

If not sounds like you may have nicked the outer casing of a wire ??? Either way I've got a multi meter and a decent working knowledge of electrics!?!?

 

E

estranged

Joined Aug 2009

168 Posts | 0+

Discussion Starter
• Oct 25, 2013

• #13

Didn't cut any wires for the led unit, only cut wires for indicators.
Do you reckon it would be a dodgy earth on the rear end as the headlight bulb only comes on when a rear light unit is fitted, or could it be anywhere on the circuit?

You are closer Mr Andy, but no way of getting bike to you as no mot or tax (because of no mot)...

 

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Andywhedd

Joined Jun 2013

87 Posts | 0+

Essex uk

• Oct 25, 2013

• #14

Ok fair enough, yeah I reckon it'll be that somewhere. It's worth just taking off seat unit and checking all the wires over, I'm not sure where the main earth is on a Millie as I've not had to fine mine yet but if you can google it or I can check the DVD manual. When you fine it make sure there's no corrosion and grease it up with a conductive grease.

 

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Andywhedd

Joined Jun 2013

87 Posts | 0+

Essex uk

• Oct 25, 2013

• #15

Try this link

http://apriliarsv.com/aprilia-rsvr/8310-bike-cutting-out-maybe-bad-earth.html

 

Slackey

Joined May 2013

111 Posts | 0+

Tattershall

• Oct 25, 2013

• #16

When you say the same bulb stays brighter do you mean the actual same bulb or the same side on the light unit? I.e. The left lamp is brighter, you change the bulbs over and then the right lamp is brighter?

 

E

estranged

Joined Aug 2009

168 Posts | 0+

Discussion Starter
• Oct 30, 2013

• #17

Same bulb as in the bulb itself. Was thinking it might be a broken filament, but it looks ok. If the brake light filament was broken, would the rear light filament be used instead? If that makes sense

 

Slackey

Joined May 2013

111 Posts | 0+

Tattershall

• Oct 30, 2013

• #18

If it is the same bulb then you have a knackered bulb. It can look like the filament is fine but it is not. What could be happening is the filament gets hot, drops a bit and touches the other filament causing the issue. Try removing the dodgy bulb and see if the light still comes on with the brakes. If it doesn't then simply put a replacement bulb in, job done.