If you follow all the procedures outlined in this thread in order you shoud be able to pinpoint the problem. To summarize:

-Check integrity of both fuses
-Check 3 wire connector behind the brake boster

If those are both OK, then your fuses and dash switches are fine and you have isolated the problem to either the blower motor or the blower regulator.

-Check the blower motor (good idea to check the integrity of the wires leading to it as well)
-Check the blower regulator