2006 cobalt ac blower will not come on

i have replaced the motor and resistor but still nothing. 12 volts present at motor connector until connected to motor then nothing. checked all associated relays and fuse with no luck. i just cant figure this on out. any ideas?kilgrinus

Do you have a diagram of the AC circuitry?  Or a picture of the page of the shop manual?

This could be a can of worms, some vehicles will run 12v ign+ to the motor then feed the ground back through a resistor circuit (the rheostat) others will feed 12 volts to the rheostat and switch through to the motor with the motor grounded, other wise  more modern vehicles use the climate control processor to do this, so tell us what vehicle, if it's US Mr. Idiot will know better than me. Thre point is you have to see what it's supposedly doing, PS have checked ALL the fuses?