Blown fuse and transmission problem

1997 Ford F150 XL, 4.2 ltr Engine, Auto Transmission, 147,000 miles. When I start my truck the fuse that controls the air conditioner/heater blows. Also transmission overdrive light on gear shifter blinks on and off. Replaced the shift control module in transmission and had check engine light reset. After a few miles, same transmission problem comes back. Was told by mechanic that air conditioner compressor was bad and that was blowing the fuse. Disconected the wire from air compressor and still have the same results. Is the circuit for the air/heater in any way connected with the transmission shift control module? Any ideas of where to start looking for this problem or what may be causing all of this.