Heater blows cold air on 2003 Ford Focus

My heater use to blow cold air just when I was stopped at stop lights, or just idling. Now, it blows cold air all the time. I took it to a mechanic, but they "could not duplicate problem." What could it be?

by in Grand Junction, CO on February 21, 2009
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2 answers
ANSWER by , February 22, 2009
Try filling out this diagnostic sheet next time you take the car in to the shop, it may help the mechanic find the problem. http://repairpal.com/blog/Heating-And-Cooling-Issues
ANSWER by , November 28, 2010
Open Hood and check for Vaccum leaks.