Directional Flasher

Agree. Put in a set of 1034 or 1157 bulbs, whichever is called out in the shop manual for your year and model.
Yes people subsitute 1157 for 1034 but the current draw isn't quite the same which effects the rate of flashing.

If the hazzard is easy to access, as shown in the linked thread, use a voltmeter to see if it is getting power. Hazzard switch should be hot all the time so when its on there should be power at the flasher unit input terminal. Go from there.

The flasher units themselves are normally closed switches. Then electric current flows through, it heats the bimetal which then bends opening the connection. So with no current, haz switch on, there should be battery voltage on the output terminal of the flasher unit. If not, the bimetal is stuck open. If so, then its not the flasher unit.