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I've been reading through most of the replies in this thread regarding the heater fan problem. I have a 2004 Ford focus 2.0 Ghia (1998-2004 version) with the Electronic Automatic Temperature Control (EATC). Recently I noticed that the heated air from the vents suddenly turned cold after around 1/2 hour into the journey. To get the heat air back, I need to increase the temperature to the highest (H1). The fan speed is kept low throughout. Does anyone knows what's wrong with my heater/fan?

I would appreciate if someone could point me in the right direction regarding my problem.