I can't figure out why my a/c is not blowing. It comes on when it wants to. I replaced the blower motor resistor last year. Yesterday I pulled the blower motor out and changed it to a new one. I installed the new one and it didn't come right on. I hit the unit next to the blower motor and it came on. But when I turned the key off and restarted the engine the a/c didn't come back on. If it is a short under there, where should I start? Any ideas should be helpful

 

Sounds like a bad electrical connection or maybe plug. Bad motors are notorious for melting the plugs and wires, start tracing the wires for shorts.