sr50 rear light

knitinglee · L Plate Warrior Joined: 13 Apr 2014 Karma :

Hi all,
I have just got a 2004 aprilia sr50,great bike so far,but one problem I need help with is the rear light,it hardly glows,just a faint glimmer,not enough to pass an MOT,no problem with the rear brake light,front lights are great,everything else electrical works fine,new bulb fitted,earth checked,connector block checked all fine,any advice with further checks would be great,thanks mandy.

Vincent · Banned Joined: 16 Oct 2006 Karma :

Does it get brighter when you rev the engine?
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Jelle · L Plate Warrior Joined: 07 Sep 2015 Karma :

If you have a dc-voltage tester you should measure about 12 volts between the taillight and earth.
Since U said the earth on the lightbulb is fine, my guess is that theres not enough volts arriving at the taillight. This may be caused by a faulty wire leading to the taillight.
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knitinglee · L Plate Warrior Joined: 13 Apr 2014 Karma :

Hi again,
No it doesnt get brighter when revd,there isnt enough power coming to the rear light,the brake light works fine,but very little power to the rear light,a fault in the wiring is my guess,I can follow the yellow power wire until it runs into the loom,at the rear,but where will it come out,and what is the next step to check please,thanks mandy.

Jelle · L Plate Warrior Joined: 07 Sep 2015 Karma :

Search the internet for an electrical schedule, that makes it a lot easier to see where everything is going.
I took a quick peek at one and saw that the yellow wire leads to a connector together with the blinkers and plate light before it goes into the loom.
Start by disconnecting this and measuring the volts at the connector, if U measure around 12V, than the problem is in the wiring behind the connector. If you already have low voltage at this point, the problem is situated in front of the connector and that wont be as easy Smile

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Speed Kills... But It Sure Keeps U Awake!

knitinglee · L Plate Warrior Joined: 13 Apr 2014 Karma :

Thanks for your help everyone,one further thing I noticed about the rear light is that it is a lot brighter when I put the main beam on,it only goes dim when the dipped beam is on,any ideas ????,thanks mandy.