Originally Posted by Dgschaadt
MrMark, great response,
I have a 2002 Itasca, just changed the rear tail light assembly. Everything worked prior to exchanging out the entire fixtures.
When I changed rack light fixture, left and right, I changed 1 wire at a time to be sure I made an exact change out. After finishing everything worked, running lights, blinkers left and right, emergency flashers but not the brake lights. I know I need to do a fuse check, but thought to reach out to the community in the event I missed something?
The Emergency flasher filament, the turn signal filament, and the brake light filament are all the same filament inside the bulb. If one works then the "light fixture" is wired correctly and is properly grounded (assuming they are lighting brightly as they are supposed to do).
It is possible for poorly grounded lights to light through the parking/running light filament - but the light will not burn bright (most evident with tungsten filaments - not sure what will happen with LED's but likely similar).
Similar holds true if one fixture is poorly grounded and it tries to get its ground thru the other fixture.
If the Emergency flashers and turn signal lights are working properly but the brake signals are not, I would be looking under the dash for issues with the brake light switch and the electrical interface between the flashers and turn signal switch (the brake light signal has to go thru the turn signal switch and the flashers to get to the back of the coach).
You didn't say what chassis your Itasca was on, but there were some Workhorse chassis that had some turn signal switch issues as well as ignition switch issues.