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Old 08-01-09, 08:43 AM   #41
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Default Re: Why do my lights get brighter when I rev the engine?

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Originally Posted by yorkie_chris View Post
Re. the "when you rev the engine" comments... last time I checked, I seem to remember my alternator putting out around 40VAC (open circuit) at tickover. So, the regulator is always in action and needing to do it's stuff.
That's when there's no load, when connected the voltage will drop significantly.
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Old 09-01-09, 11:40 AM   #42
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Default Re: Why do my lights get brighter when I rev the engine?

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Originally Posted by Baph View Post
By upgrading bulbs (eg, Osram Nightbreakers as stated), the bulbs are designed to glow brighter. This is accomplished by drawing more current due to lowered resistance in the coil. If the alternator isn't putting out maximum current (for the bulbs) they will be dimmer than they can potentially be. When the current raises (by revving the engine), naturally the bulbs get brighter.
A 55W bulb, is a 55W bulb... no matter how bright or dim it is... put 12v through it and it'll draw about 4.6 Amps.

[Edit] Just to add... what makes a bulb 55W is a factor of its restistance, and the voltage that is applied to it, as demonstrated by the simple equation: I=V/R.

The headlight is rated 55W at 12V... which means its resistance is approximately 0.2 Ohms. Since the bulb's resistance is constant (for the sake of argument), only a reduction in voltage will cause the current to drop.

So for the bulb to get dimmer... it must have a varying voltage put through it. Enough... I'm bored now.
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Last edited by BillyC; 09-01-09 at 11:45 AM.
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Old 09-01-09, 08:05 PM   #43
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Default Re: Why do my lights get brighter when I rev the engine?

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A 55W bulb, is a 55W bulb... no matter how bright or dim it is... put 12v through it and it'll draw about 4.6 Amps.

[Edit] Just to add... what makes a bulb 55W is a factor of its restistance, and the voltage that is applied to it, as demonstrated by the simple equation: I=V/R.

The headlight is rated 55W at 12V... which means its resistance is approximately 0.2 Ohms. Since the bulb's resistance is constant (for the sake of argument), only a reduction in voltage will cause the current to drop.

So for the bulb to get dimmer... it must have a varying voltage put through it. Enough... I'm bored now.
Simplest things to remember is fundamental electrical formulas.

V=IR I=V/R R=V/I. (Ohm's triangle) and P=IV(and the cos of the angle but it's generally ignored) or P=V^2R. As long as you know those you should be fine.
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Old 09-01-09, 08:22 PM   #44
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Default Re: Why do my lights get brighter when I rev the engine?

This may have been mentioned earlier. Sorry if so...

My headlights also differ in strength depending on the revs. When i'm stopped at lights for example the dash lights are almost flickering as if on thier last legs but when i get going and rev the engine they stay quite bright and at a solid strength. Is this just a part of the SV's electric or something to think about???
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Old 09-01-09, 09:10 PM   #45
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Default Re: Why do my lights get brighter when I rev the engine?

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This may have been mentioned earlier. Sorry if so...

My headlights also differ in strength depending on the revs. When i'm stopped at lights for example the dash lights are almost flickering as if on thier last legs but when i get going and rev the engine they stay quite bright and at a solid strength. Is this just a part of the SV's electric or something to think about???

i'd say if your worried check the voltage on the output of the rectifier if it's 16v + be prepared to replace to save a battery + breakdown etc . .
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Old 10-01-09, 07:42 PM   #46
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Default Re: Why do my lights get brighter when I rev the engine?

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My headlights also differ in strength depending on the revs. When i'm stopped at lights for example the dash lights are almost flickering as if on thier last legs but when i get going and rev the engine they stay quite bright and at a solid strength. Is this just a part of the SV's electric or something to think about???
Read my posts above, at tickover the system voltage can drop below the battery's voltage, thus the battery's level of charge/condition will be the important factor, but clearly a check of the charging system is in order. Do you have any actual electrical problems? Assuming not, my first thought would simply be that your battery is a bit tired, it's output voltage is simply a bit lower than needed to keep everything bright.
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If an SV650 has a flat tyre in the forest and no-one is there to blow it up, how long will it be 'til someone posts that the reg/rec is duff and the world will end unless a CBR unit is fitted? A little bit of knowledge = a dangerous thing.

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Old 15-01-09, 08:04 PM   #47
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Default Re: Why do my lights get brighter when I rev the engine?

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Originally Posted by thor View Post
Perhaps the battery is on it's last legs? I have some heated grips on, but that's it.
Also, The top half of the brake lights are dimmer than the bottom half. They also get dimmer when the indicators are on.
Any help gratefully received as always...
Maybe I have missed something, but I can't see where Thor's original observation was explained???? Unless it was covered by Soulkiss's comment that "pre K5/6 have this fault".
As you can guess, I have this peculiarity on my K3
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Old 15-01-09, 10:34 PM   #48
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Default Re: Why do my lights get brighter when I rev the engine?

Bloody hell - Leigh!

Where have you been all this time?
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If an SV650 has a flat tyre in the forest and no-one is there to blow it up, how long will it be 'til someone posts that the reg/rec is duff and the world will end unless a CBR unit is fitted? A little bit of knowledge = a dangerous thing.

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Old 15-01-09, 10:45 PM   #49
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Default Re: Why do my lights get brighter when I rev the engine?

What?? Is it doing it a lot or something? They all do this, cars included.
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Old 16-01-09, 08:43 PM   #50
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Default Re: Why do my lights get brighter when I rev the engine?

Helllloooo SS, can't get about so much now due to increasing age
Regarding the rear light, I understand the flickering at low revs, its the bottom half being brighter than the top half, especially when the indicators are working.
If this is a well known fault I'll change it, but just needed to clarify the point.
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