How to install blower motor relays??

Trailbeast has been great helping me with this but more info is always good. I decided to install the relays in the wires just behind the switch. I am confident that I am wiring the relays correctly. My car has a 3 speed fan, low comes on when the A/C or heat button is depressed med and high are controlled by the fan switch. I am seeing a low voltage at the med and high wires at the switch when it is in low position. Where is this coming from? Is it coming thru the resistors?