This is a general procedure to troubleshoot the blower circuit. Some of the tests may apply to things you have already done but if you go through them step-by-step you should find the problem.
Make sure the blower motor tests good by putting 12v & a good ground directly to the motor. If good:
Make sure there is power to the blower motor, and then everything from there is through the ground side. The ground path is from the blower to the resistor (except high speed which bypasses the resistor), to the speed switch (which directs which path through the resistor), to the mode switch (which closes the ground path in all positions except off which is the only position the blower is off) to ground.
After making sure you have 12v to the blower motor & good contact there you have to find where you are losing ground, which with 12v to the motor & a good motor, is what will keep it from running. You can jump the motor to ground to be sure the motor & connector there is good then work down the circuit. But when you lose all speeds the connector at the mode switch or the mode switch itself are the most common places of failure so check the 3 wire connector there for melting & signs of excessive heat then jumping the green & black wires from that 3 wire connector there is a good place to start after verifying that the black wire is grounded. When the mode switch is in any position except off it grounds the dark green wire through the black one. If jumping those wires (key on) gets all speeds & the connector is good the mode switch is bad. If no speeds, move to the speed switch. Check that 5 wire connector as you did for the 3 wire one. If you ground each of the 4 wires not including the dark green one (that goes to the mode switch) you should get each of the 4 speeds as long as the key is on. If yes, the speed switch is bad. If grounding the speed switch wires doesn’t get the blower running, especially high speed, go to the blower motor connector & recheck it carefully. If you do get high but are missing 1 or more of the lower speeds, the resistor is bad.
If you don’t have power to the motor check fuse 8 behind the glove box & fuse 1 in the PDC in front of the battery. For ’99 only check fuse 11, not 1.