If you bypass the switch and the lights come on but not when you step on the brake, replace the brake light switch. Jumpering the switch will keep the brake lights on all the time. Not good.
But you metioned the dash lights. Are you reffering to the park/tail/running lights? These feed from a 15 or 20 amp fuse to the headlight switch, then to the lights outside, and back into the headlight switch resistor that you turn to adjust the dash light brightness. From there it goes to a 5 or 8 amp fuse, and then to the dash lights.
Althought the brake lights and tail lights are in the same lense and same bulb, they are completely different. There are two seperate filiments in the bulb, and act like two different bulbs.
If it's the tail lights, see if the front ones are working also. This is a good bit of info.
Also check the grounds from the rear lights. If they are not grounded well they can create a feeback thorugh the opposite circiut. Brakes ground through running lights, and Vica Versa. When both are on the ground is lost and the lights go out. Perhaps you lost a ground on the side that does not light.
Do some side to side compairsions of brake lights, turn signals, and tail lights. See what is bright, or not so bright, or out. Pay attention to what combination of lights does what. This lights with the turn signal, but does not flash, etc. Then let me know. It will go a long way toward helping find the problem. The more detail on the lights behavior the more I can pinpoint the problem. Dont forget to look at the turn signal indicators on the dash. What they do in each combination helps me as well.
The park lights are a brown wire. The left turn and brake in the rear is a yellow wire. The right turn and brake in the rear is a dark green wire. Black is the ground. The backup lights are light green. The dash lights are grey. The feed to the brake light switch is orange, and it's white to the turn signal switch. The white wire is the only seperate brake light circuit. All the brakes, turn signal, and 4 way flashers all come from the turn signal switch to feed the outside lights.
Let me know what you find in detail, and I can tell you where to look.