Oh, brother, the proportional type is messing this up now. Copy my last message, past it into "notepad" if you're running windows. It should appear correctly. Basically you're taking the 12v from the A/C clutch feed, running one copy of that straight to a relay contact, while the second copy runs through the resistor (as originally supplied by your mechanic) to the other contact on a relay. The relay coil is energized or not depending on the position of a switch, fed by main A/C feed (preferably not the clutch but the coil feed for the main A/C relay).

The relay should be single pole, double throw, ie 2 contacts one of which is connected to one contact or the other depending on whether the relay is energized.