Edelbrock Carb Choke Help

[trucknut85]

Truck: 1985 chevy K10 with 5.7L
I have an Edelbrock 1406 carb with electric choke that i have hooked into the factory choke wire (light blue) that runs from the oil pressure switch. First question, will the factory choke wire supply a full 12V of power to choke when oil pressure switch is activated? Second, with the key in the on position (truck not running) the factory choke wire (light blue) is already showing voltage. Is my pressure switch wired wrong, as i didn't think there should be voltage until there is oil pressure. Or is the pressure switch faulty thus letting voltage thru regardless of whether the engine is running or not. The choke negative side is grounded to the alternator bracket. I know you can just run switched 12v from fuse box to power the choke, but i'd like to be able to leave the key on without the coil heating up.