I think thats how they are wired on most cars nowadays,but looking at a wiring schematic will be the best way to see how its done..
Here's a story about an oil pressure switch that was hooked up to a fuel pump,maybe one like this VEGA had,would work..
My sister had a 74 Vega that had one of the first "in tank" electric fuel pumps..one day in '76,it stalled about a mile from her house,so I dragged it back with a tow rope,and replaced the pump--had to drop the gas tank,it was a sucky job!..ran great again,thought that was the problem--until it died about ten feet from where it stalled two days before!..in the middle of January,no less..
I figured the pump was defective,I dropped the tank again,and the parts store handed another pump over under warranty--(never thought to test it on a battery though!)--again it started fine,and I drove it 15 miles with my sister following me,with NO troubles!..
I thought it was fixed for good...WRONG!..next day it didn't even back out of her driveway before it stalled,and refused to fire up again--silence when I listened for the pump,it wasn't working!..I beat on the tank with the key on,checked the fuse,it was OK,and I had power getting to the wires on the pump--but it had THREE wires,one I guessed was a ground,the other two had power (??)..
I finally started calling mechanics I knew from working at parts stores,and two said the same thing---- "Oh,a VEGA??..Replace the oil pressure sending unit!..I bet thats what yer problem is!..
I went HUH??.."yup,it runs the FUEL pump too,even if the "OIL" light works right,the portion of the switch that cuts power to the fuel pump can (bleep) up!..we had a few drive us NUTS till we figured THAT out!..see if it looks melted where the contacts are the wires plug onto,or if they are loose--if you can wiggle them,its JUNK!..
SO--I replaced the oil pressure sending unit (6 bucks!),and it fired up instantly..never gave any trouble after that..I jumped her original fuel pump to the battery,to test it--nothing wrong with it!..it gushed gas all over me,good thing it didn't ignite!..

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man,I was so ticked,all that work in the freezing snow for NOTHING!..(and 35 bucks for a pump it didn't even NEED too!)..
