I have the schematic handy! The green relay goes next to the yellow one, the black one goes in the corner by the fuses. You can test the black relay with some jumper wires and a meter(DMM), connect a 9Volt battery to the pins 1 and 2, it should click, and 3 and 5 should have about .5 ohm across them or less. The green relay should NOT actuate if plugged into the socket for the black high speed relay, according to my ford schematic, makes me think your green low speed relay is stuck, check 3-5 pins. Check if the fan rotates easily, as well. Check wiring.
