Power wires for sending units on 70 Stang are "ON an OFF"?????

[bullfrog66]

Howdy ya'll, My neice has enlisted me to help her with her lil toy, 1970 Stang, 351C, automatic. She just had the engine swapped out from a 302, to this 351C, they had fun with the mounting brackets. Well, here is what I have--while I was hookin wirin harness to Coil, and sendin units, checked power with a test lite and coil wire was hot with key on, sendin unit wires power was blinkin on and off. Was the wire harness book said ta use- the flat-three-wire-plug, dont recall color code right off. Went ahead and hooked up, fired up the engine and checked wires again with engine runnin, they were still blinkin, anyone know why? Are they suppose to blink? Well the wires dont blink my test lite is whats doin the blinkin. I am no mechanic, jus a ol shade tree type. Any advice and help would be preciated, Thanks Bullfrog