Does your high speed work?
If so, it's most likely your low speed resistor that has gone bad. I'm surprised that no one else has mentioned this.
The resistor is on the lower driver's side of the fan shroud.
Also, if you get some non-insulated 12 guage quick connects, you can make a small jumper to bypass the relay for testing.
I really doubt that the relay is bad. They are really heavy duty pieces.
HTH,
BP
