I have a 1979 K5 Blazer with power windows. The rear window will go down from the dash switch, but it won't even try to go back up. It goes up beautifully when I hook the cable to a cordless drill. Is this a motor issue? Transmission? If not, what should I look for? I'm not much good at power-window issues.

 

broken wire maybe? its been a while since i messed with k5 power windows but if i remember correctly the motor grounds to the tailgate and there is two wires, one positive for up and one for down. possible that one of those wires is cut or disconnected causing it not to go up. try using the key in the gate too to get it to go back up. or run your own 12 v source to each wire to see if it will work if you by pass the switch

 

Could be a problem with the switch in the dash as well. They will collect gunk and dust over the years and the contacts will get clogged up.

Have you tested any of the wiring connections with a multi meter to see if you're getting juice? Might need to have a friend hit the button while you curl up in the back with the tailgate closed.