Heater blows cold air on 2004 Ford Explorer

When I turn the heat on I can hear faint knocking sounds coming from the dashboard. The heater only blows cold air. The air conditioner works fine. What could the problem be?

by in Tulsa, OK on October 12, 2009
3 answers
ANSWER by on October 12, 2009
There are many variations to the heater controls depending on options, engines ect.....The heater has vacuum operated actuators that move heater flaps any of which could fail or loose a vacuum hose attached to it which would effect proper heater operation. The heater control valve is in the engine compartment near the firewall toward the center rear of the engine ensure the vacuum hose is attached to it. If you fell competent to doing some of the tests yourself, Autozone have some popular vehicle workshop manuals free on line on there website or there is a company that independent auto repair shops "buy" their information from that offer a very reasonable service to do it yourselvers. You get a one year subscription to year make and model specific repair procedures, service bulletins, component locations, wiring diagrams ect.... great quality information same as the professionals have ,much better than generic workshop manuals from parts stores, much cheaper than the factory manual. http://www.alldatadiy.com/
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ANSWER by on December 30, 2009
1997 ford explorer is the control valve for the heater in the same location as the 2004 if not where is it located 4.0 v six
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ANSWER by on March 24, 2010
I have the same issue seems to be a design flaw if so many are having the same issue.
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