I have a 2002 Sedan 4cyl. I have the heater/blower problem where only number 4 works ( 1,2,3 nothing). I am picking up the resistor pack tomorrow.

Next problem, the heat works great except when I turn on the lights......it blows cold out from the front defroster whenever I turn on the headlights. Also, the rear defrost only work if the head lights are off. I cant drive at night if its cold cause the windows fog up so bad I cant see.

Does the resistor pack have something to do with this?

I have recently replaced the battery.