New bulb cost a couple bucks. Buy one, replace the bulb, then if it still does not work, return for ideas. Don't make a bad bulb more work than it is. If the one bulb in the light assembly is flashing and one is not. It is 99% a bulb problem.
New bulb cost a couple bucks. Buy one, replace the bulb, then if it still does not work, return for ideas. Don't make a bad bulb more work than it is. If the one bulb in the light assembly is flashing and one is not. It is 99% a bulb problem.
If it is the wiring at the socket, then your ground is good and the power lead to the low filiment is good (because you said the bulb lights up when the headlights are turned on). It is possible that the power lead to the high filiment is loose or not getting power (which is why the bulb does not light for turnsignals or hazards)
Could also be a problem with the actual contact in the bottom of the socket. Sometimes, the contact will wear to a hollow shape and even a new bulb will not make proper contact. As mentioned, get out the meter and check for voltage.