My mother-in-laws 2000 Toyota Corolla stopped flashing all it's turn signals. It would work one minute then not the next. The hazards worked intermittently also. Bulbs all good. Electronic Flasher good. Hazard switch good. Turn switch good. 7.5A fuse good. 12V at Flasher. Ground to Flasher good. When you select left or right or hazards, you hear the flasher clicking rapidly but no lights at all. I know, you think it's the bulbs? No!
The electronic flasher is the key to this problem. It is designed to measure the resistance on the line to the bulbs. If the value is below about 1.2ohms (all bulbs good on that side or both side together when hazard selected) If OK it activates it's relay to the bulbs at the normal 1 sec flashing rate you are used to. If the value is ANY higher, it simulates the "bad bulb" condition that the old bi-metal strips showed when the load dropped due to an open bulb, a fast half second flashing.
I measured the value at the bulbs on one side 1.2ohms! But at the flasher (with the hazard switch or the turn switch selecting a side - 9.8Kohms! So where is the problem? The Green/white wire from the center pin of the flasher is supposed to go to both the hazard switch AND the turn switch.
Getting to the hazard switch is 1000 times easier than the turn switch on the stalk of course.
Pulled hazard switch out. (The cover just pulls off with the vents.) ran a wire from the center pin of the flasher (its case separates easily) to the green/white wire on the hazard switch.
It fixed it.
Why didn't I pull out the white plastic panel near the drivers left foot that held the flasher? You try it - the darn thing is held in by the main loom and 10 connectors. I did try, but finally just ran an extra wire, routing it safely away from the drivers legs and pedals.
Goodness knows what the dealer would have wanted for this fix. I don't dare think of it.