What year / make / model bike are you working on?

 

good point....06 Shadow Aero 750

 

Are you checking with a test light or multimeter or just visually checking the wires? Have you checked the ground to the housing?
Sometimes the filliment in the bulb will break but visually checking it still looks good.
For the price of an 1157 bulb I would install a new one before taking it to the shop.

 

Yes, dgraves. I tried a new light bulb. No difference

 

If the front turn signals are also operating correctly as running lights with the key on or when running, you can use either of those known-good bulbs to troubleshoot the tail/brake light on the rear. Your rear turn signals don't operate as running lights in most stock configurations.

Start with the cheapest, most obvious possible problem to rule out simple solutions before going on to complex, expensive ones. If your front running light / turn signals work correctly, then you know the circuit is likely intact and the problem is likley isolated to the rear brake / running light circuit.

Bulb, ground, electrical connections, fuses, etc.

CB

 

Your rear turn signals don't operate as running lights in most stock configurations.
CB

This was my first thought. Which lights are not working? Does the tail light function as a running light (it should)? As said above, the rear turn signals most likely are not running lights but turn signals only (in stock form).

 

I have video of all the lights working with the bike running. Like I said before, they still work when applied, turning and braking. They just don't stay on as running lights anymore