To my knowledge the AC compressor should not turn on with the heater except for just the defrost mode. However, Ford does things differently than everyone else, and the Focus is different than most other Ford products. They might have designed it to do something I'm not aware of. Regardless, you're right, logic dictates replacing the tensioner shouldn't be the cause of the problem, but I've been fooled by my logic many times. My best suggestion is to look in that area to see if a vacuum hose became unplugged or loose, a sensor became unplugged, or something like that.
Double-check the belt routing. Even if it's wrong, it's unlikely the AC compressor could be made to run backward, and even if it did, it would still work properly. I can't think of anything that would cause this problem, but sometimes I have to find what I did wrong, THEN figure out why it caused the symptoms it did.
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Saturday, January 26th, 2013 AT 11:26 PM