Tailights (parking lamps) come on with headlights (autolamp or manual) BRAKE LIGHTS are for WHEN you step on the brakes , they are brighter than the taillights even if they're the same bulb. SO what I guess I'm asking is not going to make sense. You say "all work , but not together" , Are your brake/taillight bulbs a single filament bulb that is current controlled for breaking? or are they dual filament bulbs? different troubleshooting for each system.
One bulb shiwed no sign of burnt out. The other had the socket missing. Bought replacement socket from dealer and two new bulbs. Had to clean contact . After cleaning they both worked but now dont if headlamps on. Ps, thx formcontacting me. Didnt pass inspection three time n runing out of time(and patience)
Make sure the power at each point has power when 1, tail lights only when they are on 2, the other is powered only when brakes are applied. Then check to see if there is a good ground to the sides of the sockets. Sound like they are feeding back to each other to find a ground, check for a good ground, not at each pin, but the case.