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TAK79's Avatar
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01-30-04, 06:45 AM   #1  

I have a 98 Ford F-150 with a V8, and my heater isnt working properly. The blower works fine and there is no noises or anything. It does blow out kind of warm air when driving but when I stop the warm air then turns to cold air. Then back to kind of warm air when driving again. The engine runs at normal temperature and everything else seems to be allright. Any suggestions???

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davo's Avatar

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01-30-04, 03:20 PM   #2  
Make sure the coolant is full and flush the heater core.Sounds like low coolant or a blocked core.

Pendragon's Avatar

Join Date: Jul 2002
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01-31-04, 08:45 AM   #3  
Try this:
When you're stopped, rev the engine. If the air gets warm again, this is my guess..

Your dampers are vacuum controlled, and you've got a leak in one of the lines so that whenever you stop, there isn't enough vacuum to keep the damper pulled to the heat setting.

mike from nj's Avatar
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01-31-04, 10:40 AM   #4  
mike from nj
quite the opposite pendragon.

at idle, the engine's vacuum is highest.

when you rev the engine, you are speeding up the coolant flow through the engine(from the water pump) and heater core too. if there is any air or a partially blocked heater core, this will help it out a little. back down to idle and the coolant slows down and the heat diminishes.

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