rear brakes lights always on but only when lights are on. please help

[tweed]

Right so normal day driving rear brake lights work fine.
When driving and turning on side lights I loose power, even if I put my foot flat to floor. Quick lift if the pedal and back on and its fine.
But with the lights on the rear brake lights are constantly on, all three. Its as if power is sent to brake lights instead of night lights. Makes no difference if I push brake pedal or not.
I did discount both rear lights and the centre boot brake light then started to work as normal (lights still turned on)

It does have something wired in, its got light bulb bypass wrote on the box and has a fuse. I pulled out the fuse but still no change.

Any ideas?

 

[tweed]

It has a towbar so the bulb failure bypass could be for that?

 

[Audi Doodah]

Dodgy headlight switch or brake light switch

 

[tweed]

Brake lights work fine with lights of so wont be that.
And I cant see how a faulty headlight switch would make the rears brake lights stay constantly on but the headlights work perfectly fine.

Is there fuses or relays I can check? Earth for lights?

 

[Audi Doodah]

Trust me, I know it sounds daft but I've read about them causing all kinds of problems. A faulty one can even prevent the car from starting. Links to your loss of power when you switch the lights on.

Brake light switches can cause problems with false bulb out indications and brake lights always on

 

[tweed]

Ok bud ill try that. Cheers