Turn signal-brake light question

[1000national]

I've got a unique (for me) issue on a 1998 Chevrolet Silverado pickup. The right turn signal flashes fast (like a bulb out warning) but all the bulbs test good.
If the headlights are turned on...the right rear brake lights work, if the headlight switch is off...no right rear brake lights.
Unfortunately, the headlights being on don't allow the
right rear blinker to work or I'd just drive around with the headlights on. Also, the hazard lights are not blinking
either...whether or not the headlights are on. They just
indicate a steady light on the dashboard indicator.
Someone please help........is this a sign of the turn signal lever switch? What else have I missed...I've looked at the wiring and the sockets...and tested the bulbs.
Thanks,
Steve

 

[evelrod]

These seemingly non connected events are often, in actuality, connected by one or more bad ground circuits. I would start with that assumption first and work toward the more complicated 'part failure' analysis should it not be the underlying problem.

Rod

 

[sreid]

I'm with evelrod, first check the battery ground strap to the frame. Hard to check, but the ground for the dash board printed circuit board (sometimes just a mounting screw).

 

[rmw]

You might have a filament of one of the dual filiment bulbs in the circuit that has broken and is shorted to the headlight circuit filament or its metal parts. Take the bulb(s) out and examine them up close. Some times the bulbs can check good under these conditons but exhibit the symptoms you describe. when it is working, it is finding its ground though the headlight circuit.

rmw