I have the same problem except the fan only works at #4. I don't even know how my climate control works since this has been broken on the car since I bought it. I replaced the blower motor resister, (under driver side kick panel, reach in toward the center, ask for further instruction if you can't find it.). It then stopped working a week later. What the heck? Replaced it again, maybe a dud part. Stop working a week later again. I gave up. I'm thinking at this point it might be a bad relay providing too much power shorting out the blower motor resistor, OR I need to replace the blower motor because for whatever reason that is sending too much power to the resistor. Either way, the resistor keeps getting blown. The final stage unit? What is that? Anyway, I hope this gives you an idea of what you're running into, perhaps we can solve both our problems together
. Good luck.