Check the fuse panel, is located inside the glove box, on the left side fuse box, according with this diagram...
HTR / A/C ==>> Heater/Air Conditioner Blower Controls
INS LPS ==>> Heater and A/C Control, Defog Switch (and others)
According with your previous diagnostic, could be some ground issue in the wiring connections. You either have a bad new blower motor resistor, a bad control head or a bad blower motor.
I think the first steps I would take would be to remove the blower motor
and clean it. If it has never been done it wouldn't hurt it anyway.
When you get it out you can then check to see if there is a lot of play
in the motor shaft. If there is then you might just want to replace it.
If
it looks good and is clean then that is probably not the problem. The
nest thing you should do is remove the control head and inspect it. See
how the connections are and if they are in good condition. If they are
not then you might need to replace it if you can't clean them.
Addionally, I suggest read this articew about compressor clutch toubleshooting:
aa1car.com/library/2003/ic50350.
Hope helps; keep us updated.