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johnny
02-17-2014, 08:57 AM
Re: '98 Ford F-150. The a/c will be working for a good while then something shuts it down and the heater begins to work. I can hear something inside the panel area open or close when this happens.
RhinoZ24
02-17-2014, 09:52 AM
What's your temp gauge look like? Does it start moving towards hot right before this happens?
johnny
02-17-2014, 10:41 AM
It cools great but then something sounds like it shuts or closes and the heater comes on. The sound is like a suction then it closes bringing on the hot air. I tried messing with the switch that changes ac to panel and then off and floor. It seems to work. After awhile of messing with it works again. Its like if there is something that closes and changes to heater.
RhinoZ24
02-17-2014, 02:08 PM
Is there any clicking noise or anything in the dash when this happens as well? If so, it sounds like your blend door actuator is malfunctioning. It closes off the A/C vents and opens up the heater vents (that would be the closing and suction sounds you are hearing).
johnny
02-17-2014, 03:09 PM
Yes that is exactly what it does. Closes the a/c and opes up the heater. So this blend door actuator is what needs replacing?
RhinoZ24
02-17-2014, 03:48 PM
Sounds like the culprit then, and I'm not entirely sure since HVAC is not my specialty. However, if Joe Grasso would like to chime in, or Alex, they know more on this issue.
Raptor05121
02-17-2014, 05:45 PM
Sounds like a blend door. It is controlled by vacuum lines. So either the door or module is faulty or your vacuum lines are failing. Ford designed the HVAC for the fail-safe setting to go to defrost. (IE if your system failed, it goes to defrost so you can still see out of your windows)
Jersey_Joe
02-17-2014, 09:17 PM
I agree with the professor above me ^. I had a 03 and the same thing happined. Also it would not go through the controls. It would only go on defrost. Air too. The blend door is usually the problem. However. The entire dash needs to come out. There r plenty of YouTube videos on how too. That's how I did it.

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Took me about 6 hrs start to finish.
johnny
02-18-2014, 09:36 AM
Thank you gentlemen. Your knowledge is very welcomed by me and everyone else. Have a great day!
Jersey_Joe
02-18-2014, 11:35 AM
Most welcome. Let us know how u make out bud
RhinoZ24
02-18-2014, 03:59 PM
Thank you gentlemen. Your knowledge is very welcomed by me and everyone else. Have a great day!

You're welcome, glad Joe and Alex pitched in to give you more info too.