So the very next time I drove the car after replacing the speedometer cable the turn signals failed. Emergency flashers worked, but the turn signals did not. Stoplights and emergency flashers were working fine. Thanks to page 2 of this excellent diagram I found on the Jeepster Commando Club of America forums I was pretty sure the problem was in the part of the circuit that supplies power to the turn signals. Power goes from the accessory terminal on the ignition switch to the turn signal flasher then to the turn signal switch via the hazard light switch. If I was lucky the problem was at or near the flasher. If I was unlucky the hazard switch or turn signal switch failed or a wire broke in the steering column.
Assuming I would get lucky I pulled the turn signal flasher out of the rats nest of wiring stuffed up behind the dash. The red arrow points to the flasher. I installed this electronic flasher because the LED taillights I installed do not draw enough current to correctly operate a mechanical flasher. By the way on the page I linked here I said all this wiring would get cleaned up later. I must have been lying.
First check is for power on the flasher. I am getting 12V when the key is on. So the flasher is getting power. I checked the ground wire too and it was fine. Next I removed the wires from the flasher and tied them together. Turn signals came on. Of course they don’t flash but that means my brand-new flasher broke. I installed this back in September. How much do you want to bet this has a 90 day warranty?
I rooted around in my garage and found an ancient Bosch flasher from my VW days. It is a three-terminal design with a ground terminal so I used a jumper to tie that pin to ground. The turn signals worked but blinked way too fast. I will have to buy another (different) electronic flasher. This is the second brand-new part I have had fail almost immediately. I am starting to think that maybe the quality control in China is not up to par…