Pontiac Repair: 1997 P. Grand Prix-Blower Switch controling headlights, blower motor resistor, fuse box

Question
Hi, My blower only works on High and when i turn it on high it controls my lights. I know this question was already asked and this was your response:
Answer
Hey Isaiah:

You have no air flow comming out of the vents?? If that is the case more than likely blower motor resistor has gone bad. It's pretty common on them. it's loaced in the bottom of the heater box below the glove box it has 3 screws that hold it in. when you take it out you will know right away if it's bad the coating on the resistor will looked burnt up. if so replace it with a GM part. the new part will look differnt then what you took out it is a redesigned part that will not go bad. good luck :}

:) I was wondering if this would correct the lights as well so that the lights go back to being automatic. And can I replace the part?(I know very very little about cars but if all it is, is unscrewing and screwing something else in i can do that) and do you know how expensive this is. Thanks!!

Answer
Hey Brian:

I think you have 2 issues here. I think you indeed have a bad blower resistor that's why 1-4 speeds do not work. As for the lights working with the blower motor???? I looked at a wiring schematic and I didn't think the 2 had anything in common but they do if this car has day time running lights. They share the same ground. If that ground is bad then one system can affect the other. The ground that may be bad here is behind the fuse box in the glove box it's attached to the big metal cross car brace the wire will be black or black witha white stripe on it. That is the only thing I can see that they have in common. Hope that helps you out some.
Good luck :}