The flasher itself does not need a ground source. It only helps complete the circuit connection on the hot side. When you use the turn switch, the switch itself completes the left or right light circuit, flowing voltage thru the flasher. The ground side of the exterior bulb is what fully completes the circuit on each side. Hence when a bulb is burned out, it rapid flashes being it sees half the load. On 55s, do they have a turn signal indicator on the dash? And is it a three leg flasher? Only reason I ask is that the 51 I'm working on doesn't have factory blinkers, and the aftermarket NAPA switch strapping to the stock column used a three leg flasher. One side goes to batt+, one leg goes to turn switch which will then go to exterior bulbs and third leg connects to an internal indicator bulb in the turn switch housing. Between the 2 out flasher legs, one is for the exterior bulbs, and the other is an isolated output to the indicator, but it does not help complete the circuit to the exterior bulbs.
I'm installing a complete new modern wiring harness that uses two separate 2 leg flashers. One for turn, one for hazard. The NAPA switch has a built in action to use the only one flasher to do both turn and hazard, so I've wired in the switch indicator bulb to get a signal thru a dual diode isolator from left and right signals from the exterior bulbs. The diodes keep the left signal from connecting to the right and making all the bulbs flash when just left turn on. It's kinda complicated, but a simple circuit used on single dash indicator lights such as motorcycles.
Now I think you can't mix up the two outs from a 3 leg flasher without consequences. If you do, the dash indicator light will try to complete the circuit without the turn switch used, but it won't go to the exterior bulbs.
Hopefully this is clear enough to not confuse you.
Last edited by Chip O; 06/16/2024 6:05 PM. Reason: missing words
