Headlights on. Taillights off. Backlights fine.

We had a similar issue with our 91 yj, we replaced the switch but the tail lights continued to act up. We knew someone who could read wire diagrams and went by what was in the Chilton book, we had to route the wires a certain way in order for them to work properly because the old wires had worn and faded due to the age and we're hard to figure out which wire went where.