Dash lights come on when I press brake...any thoughts?

[Greasey Fingers]

Just going over my electrics and everything works perfect except when I press the brake, the brake light comes on but so do the speedo/tacho back lights. I had this all sorted before so dunno what happened, or maybe I didn't notice but I'm pretty sure I would of.

I know that the system is all linked because the dash light come on when the running lights are on and they have to do with the tail light. The wire that is connected with the running lights is the blue with red stripe I'm pretty sure. Any thoughts on why the dash lights come on and off when I press the brakes? maybe earthing out some where?

 

[16VGTIDave]

I'd start in the headlight bucket and see if the brake light wiring (from front switch to light) is connected to the dash lights - either by a short or mis-connection. The dash lights should turn on with the key in the run position only. If they come on with the key in the parking light position, then you will have to fix that first.

 

[Greasey Fingers]

Cheers Dave, I checked the bucket it all seems ok. I think its the tail light assembly, because when I unplug the tail light assembly then press the brake pedal, the dash lights do not come on. So I guessing the running light wire is shorting somewhere in the tail light assembly when the brake is pressed and lighting up the dash lights. What do you think?

 

[16VGTIDave]

Without a wiring diagram it is difficult to say. I have seen bulbs shorted internally causing weird lighting issues. A poor ground connection can also cause issues.

 

[Greasey Fingers]

Found the problem, it was a short in the globe assembly of the aftermarket tail light I bought. I replaced the globe assembly and now the fault is fixed