Rear bulb keeps blowing

[uk750]

Ok recently I upgraded my 98+ to the 2003+ tail including using the twin rear bulb tail light, now for some reason it keeps blowing one of the bulbs, brake lights still work fine.

I leave the lights on permanently, so they're on when I start it and just turn off when i switch the ignition off. In order to wire them in I just made a loom which went from the OE 99 connector to the 2003 connector.

Could it be due to current draw (number plate light and 2 tails running off wiring designed to run one tail ? )

[rexazz2]

check the ground
a lot of light issues go back to ground
it is only one of the two bulbs right

[uk750]

Ok i'll check that but yes it's just one of the bulbs, the other tail light carries on working fine along with the number plate light

[Black_peter]

If you're running the bulbs in parallel then yes.
That drops the resistance and increases the current.
The slightly lower bulb is probably blowing/
See here:

http://www.aikenamps.com/AddingComponents.htm

[uk750]

d'oh so should have payed attention to physics and the basic laws at school !

[Black_peter]

Nah.. That's why we're here!

[The CyberPoet]

I ran the twin OEM bulbs in an 01 that I swapped tails on and had zero problems. The wiring harness I cut and spliced the 98-02 connector onto the later light's wires, running both of the bulb positives into the one end of the connection and the lead to the brake light positive feed into the other. Ran without fail for about a year before the bike was swiped...

I'd look closely at the bulb socket and at your splice-job if I were you -- might be corroded or otherwise defective. Just for the record: I spliced, braided and soldered, then covered the connection with heat shrink tubing...

Q: are you sure you got all the wires right?

Cheers
=-= The CyberPoet