The other night I noticed that every time I hit the brake peddle, my marker lights and dash lights come on! I tested it in the driveway, lights off, engine running, and they came on. Any ideas????

 

Those are different circuits, sounds like you have some shorted wiring someplace... the only single thing that jumps out to me as conceivably causing all that is your headlight switch; there's a tan (with white stripe? I forget) wire there that's a primary feed to a lot of stuff that overheats and melts, this can melt adjacent wires and cause weirdness like what you're seeing.

I'm assuming there are no wiring system mods by you or anybody else....

 

Are your brake globes dual filament brake/parker?

It's really common to have a broken filament bridged across and when you hit the brakes it back-feeds the parker circuit.

 

You have lost your ground on the 1157 bulb in the tail light housing.

The 1157 bulb is a dual filament bulb, 2 hot wires in and a single GRD which is the metal side of the bulb. If you look close when you apply the brakes you will see both elements in the bulb glow instead of just one. The parking light circuit is now providing the GRD path for the brakes. If you remove the bulbs one at a time and apply the brakes you can find the side with the bad GRD wire connection.
Also, with the parking lights ON and applying the brakes will cause the parking light side of the 1157 bulb to go out and no brakes light either as now neither filament has a GRD.

Bottom line is bad ground connection cause very weird problems.

JIM

 

Good theories I see posted but one key point is being over looked he said his dash lights come on when applying the brakes. The brake circuit and the dash lights are two separate circuits so a lack of ground could not cause a back feed like this. He might have two problems how ever.

 

The 2 separate circuits combine at the 1157 bulb to a single ground wire. If the ground wire is bad the brake lights will ground through the other filament in the bulb.

If there are 2 separate ground wires, then you are correct.

JIM

 

Could be in the headlight switch I had one fail on me on my truck I had dash lights and headlights and brake lights but no exterior lights, no license plate lights, no parking lights, no marker lights.

 

Thanks for the info! I haven't had time to check it out much but, I DO have LED tail lights installed on this truck.

 

The connection between the two circuits is a bit convoluted. Looking at the wiring diagram for my '84 (not sure of year of the subject vehicle), fuse #4 is hot at all times and feeds the light switch. From the output of the light switch, the circuit for the dash lights is routed through a second fuse, #17. This arrangement is so if a tail light shorts out, it will blow the first fuse (#4) and also kill the dash lights to get your attention. I can't remember the source, but I was taught this was required for all vehicles sold in the US. The second fuse (#17) is above and beyond what is required, and is only for the dash lights, with the idea being a short in the dash lights won't disable the tail lights.

So let's say you want to win a bar bet by lighting up the dash and tail lights without turning on the light switch. Take out one of the dual filament tail/brake bulbs. Run a jumper between the two contacts in the bulb socket. Now step on the brakes. The 12V to the brake circuit will now backfeed the dash and tail lights, even with the light switch off, and you can enjoy the drink you just won. As others have already mentioned, a loose filament inside a dual filament can cause this same effect. It's just like connecting a jumper between the two circuits.

Also mentioned, pay close attention to the grounds for any dual filament bulbs. If new bulbs don't fix it, a bad ground can cause a similar scenario. The two filaments end up in a series circuit if the ground is missing, and this also backfeeds power to the other circuit. The lights may not be as bright as normal due to the series connection, but they still light up. Been there, done that, and even got the T-shirt.