only thing in the turn sig cup likely to be a problem is the switch, but could be some bad connections at the big connector where the wires come out of the column or in that tangle of connectors under the floor

stop light power goes from the headlight switch to the brake light switch to the turn signal switch [where it is interrupted fot the side selected, if any] then carries on to the tail - if the turn signals work the problem with the brake lights is more likely in wiring ... wiring shown towards the last page here

Bill

Moved over to the Passing Lane

"When we tug a single thing in nature we find it attached to the rest of the world" John Muir
"When we tug a single thing on an old truck, we find it falls off" me
Some TF series details & TF heater pics & Rust-a-holics Unanimous parking lot