I have a '97 GSR.

With the light switch turned off, when I press the brake pedal, my clock dims, and my dash and heater panel illuminate.
With the light switch turned on, when I press the brake pedal no lights change.

As you can read above anytime I press the brake pedal the lights inside the car act as if the light switch is being turned on. This problem has come out of nowhere, it is not directly following any upgrades or mods. I have replaced the brake light switch on the pedal with no change in the lights acting up.

Any pointers? or ideas? Any help is appreciated..

 

Get a new alternator and plan on changing that one in the near future

 

Check the tail light ground, also check all the brake light bulbs, a common problem with dual filament bulbs is the filaments will "warp" over time and every once in a while the filaments will touch, if the brake light filament is touching the park light filament every time you step on the brake the park light circuit will power up, if the park light switch is on you would not notice as the park light circuit is already on, turn on the park lights and see if the brake lights are also on. 94

 

wow interesting. Never thought of or heard of that, but certainly sounds plausible.

 

Actually yes, when I turn on the running lights, the Brake lights are lit up as if the brake pedal is pressed. I'll try changing the bulbs. Where is this taillight ground you speak of? Doesn't it just ground to the body?

 

Yes the tail light ground is grounded to chassis, behind the rear trim panel, remove, [unplug] one bulb at a time and try the lights, it can be hard to see if filaments are touching as the bulb is still "good".
Also inspect the bulb socket, make sure it is rust/debris free, a bad ground on a duel filament bulb will cause the same thing

Unplug a bulb and go step on brake, when park lights no longer turn on, [when stepping on brake] you have found the bad bulb.

We, [Dave Ward Auto Electric] get one or two of these every few months, it can happen to any car that uses duel filament bulbs. 94