This flasher duplicates the original 3 terminal design which was used with the Signal-Stat 4 wire turn signal switch:

www.ebay.com/itm/303503036652?

The terminal labeled "P" on the flasher is there specifically to flash a pilot light, either on the dash, or on the end of the turn signal switch stem. The Signal Stat switch had a green light on the end of the handle which was connected to the P terminal on the flasher. I've installed a few dozen of those systems on big rigs, back in the 1970s, at a minumum. They work.
Jerry


"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
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