I have a puzzling problem with my 2011 Fusion S 4 cylinder AT with only 6800 miles. The car has the standard manual control heating/ac system. Twice recently while driving the car the heater started blowing very hot air out of the dash vents even though the temperature control was set to the cold position. I turned on the AC and heard the compressor click on, but the air coming from the vents was still very hot. I shut the car off, and restarted it, and everything was back to working properly. So I assume it was some sort of electrical problem. But here is the real dilemma. The 2nd time it happened, the transmission failed to work properly. I was driving in traffic and came to a stoplight. When I tried to accelerate the car would not move...the transmission was not in engaged. The engine sped up and there was a series of thumps and bangs as the transmission was trying to engage. Turning the car off and restarting the engine corrected the malfunction of both the transmission and the heater. How are the heater and the transmission electrically interrelated? Is there some sort of on board computer which controls both the function of the heater and the transmission?

 

I don't know if this is the problem with your vehicle or not, but,,,,,,,,,, one thing that both of those systems have in common is the main ground connection from the battery negative post to the connection on the vehicle. There were some problems with paint under the ground cable where it is connected to the vehicle. "Ford Tech Makuloco" had a good film clip that explained some of the problems a poor ground there might cause. All that was required was to remove the ground cable from the sheet metal , clean the paint from under the terminal and reinstall it with a little dielectric grease covering it when done.

 

Thanks for the suggestion. I will check the ground.