bypass back light wiring on runner

my mate has an old shape runner and when he bought it, it needed a new loom as the old loom was melted. With the new loom and 3 different rectifiers tested, the back light is still very dim. The brake light is fine. Checked wiring several times and changed bulb and its still the same. The scoot is due its MOT this weekend, so, is there a way to feed constant power to the back light bulb when the scooter is on? Tried rewiring it to the headlights but it stops them from working, so im confused. Can anyone help me?

 

The tail light is wired to the headlight as standard What voltage is it getting at the bulb?

Maybe you could take power off the brake light switch or something like that but tbh mate doing a good job of it aint really gonna be that much easier or quicker than looking over the loom properly and could make solving elec problems in the future more complicated..how it is now is best they dont spend 1000s designing these looms for fun lol

Fix it dont bodge it basically

 

tried with a whole new electrical system and still nothing has changed which i dont understand:/

 

Only thing I can think of is maybe you've got the connectors on opposite (tail live to brake and brake live connected to tail)? I did that once and the tail (on with the headlight) would be really bright and the brake light would work but was madly dim.

Have you checked it with a multimeter at all? Would make your life alot easier if you haven't yet

 

the connectors are on the correct way round, as when i pull the brake levers the bright light comes on but when the engines on or revving it doesnt work. When i unplug the headlights it works properly. Im guessing something in the headlights is draining the power from the back bulb? And yeah got a multimeter pal but dont know where to put the contacts or what readings i should be looking for

 

sounds like a bad earthing point somewhere

 

forgot to mention the headlight bulbs have been change from 25 watt bulbs to 55w halogen bulbs if that could be the reason?

 

Lol yes easily