There are three major things you need to know about the blower wiring, in addition to the fact that the fan is always on, even in the "off" position.
1. There's a ground wire. The blower and the relay are mounted in plastic, and they need a ground wire. For most engines, the ground was on the compressor brackets with the compressor clutch ground. There's a plug, called the "compressor harn line conn" in this diagram. If you unplug that, the blower will stop. If you remove your compressor brackets, the blower will stop (for most engines).
2. There are two power supplies for the blower. High speed is powered off the back of the alternator for most engines, circuit #2, red, in this diagram. There is a connector in that line, or maybe two, and these get hot and corrode. Expect problems. Lower speeds are powered by the heater fuse, which sends power through wires 50A, 50B (brown) under the dash, plugs into the A/C harness, and powers all the controls there, and eventually goes through the resistors and the compressor cold controls.
3. The relay is a double-throw. It sees a big red wire with 12V coming from the alternator, and reduced power coming from the resistors. It has to choose between those two, and connect one of those two items to the blower motor. When the coil is powered by circuit 52, it chooses high. If the coil is off, it chooses the resistors. The coil is turned on by the A/C control head under the dash.