Flashing Beacons Problem

[angus464]

Hi

Yesterday I put 2 Britax Mini lightbars onto the back of my transit connect. I connected an Earth to the body of the van and ran it down the earth spade on my switch and ran the live down the the live spade on the switch. ran the other live wire from the switch into the wire of the interior light, and i put a 15amp fuse in that line.
The Beacons work fine BUT when they are off the interior lights are very very dim, but when i switch the beacons on the interior goes back to normal brightness!
Any idea what ive done wrong?

Thanks in advance

 

[cactikid]

i would have taken the 12v feed off the fuse box as some interior lights might have a timer/dimmer.

 

[angus464]

i would have taken the 12v feed off the fuse box as some interior lights might have a timer/dimmer.

Yeah, thought about doing that but didnt really know how to go about doing it? It just seemed easier at the time to just run a wire up behind the door rubber seal to the light rather than to go under the carpet to the fuse box.