It's located in your car. Take it to a professional. If you can't even find the part (actually you don't even know the correct name for it), you definitely shouldn't be touching it.
The 1991 Volvo brake light relay switch is located beneath the drivers side dashboard. The brake light relay switch will be above the brake pedal.
There is no brake light relay. There is however a brake light switch located above the brake pedal.
The brake light switch relay for your 1997 Chevy truck is located beneath the drivers side dashboard. The brake light relay switch will be above the brake pedal.
The daytime running light module on a 2005 F-350 is located underneath the hood. The module will be in the relay box.
Change out the flasher relay located under the dash. Not the brake light switch which is activated by the brake pedal. Replacing the relay should solve the problem.
Looking at the Autozone "repair guides" ther is a relay for the 3rd brake light, but offers no help on its location.
There is more than one relay, be more specific. Third Brake light
The DRL Module is located at the LH Rocker Panel left of the brake, under and just below the dash. The DRL Module and the DRL Relay are side-by-side.
It is located on the brake pedal arm under the dash.
The 1996 GMC Sierra DRL module is located underneath the dash panel on the driverside between the pakingy brake pedal and the brake pedal.
Fuse and/or switch Switch located at upper end of brake pedal under dash
A malfunctioning brake light relay switch will cause your 1993 Toyota Corolla brake lights to stay on all the time. The brake light relay switch is located beneath the drivers side dashboard.