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1990 Sedan Deville
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18 Posts
Discussion Starter #1
:confused: I have an F40 and F49 codes. The heat turns on for the first 30 minutes and then it blows cold air. Where is the air mix door and how do you fix it? The F49 code just turned on. I'm not sure if its much of a problem right now but any help with either code will be appreciated.
 

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'87 Coupe DeVille 4.1L FWD(New engine '08) 1981 F100 '03FXDL
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879 Posts
F40 is a air mix door problem. check door for binding/stuck or out of adjustment. Check for a faulty programmer motor or loose connection to it.

F49 is a high temp clutch disengagement. The BCM will disengage the clutch when the following conditions are present: AC low pressure switch Open/AC high-side temp above 200dgF/coolant temp above 259dgF/WOT signal from ECM/open or shorted AC low-side sensor circuit

Hope this helps some.....
 

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1926 Model T street rod, 2000 Jaguar XJ8, 1999 Corvette.
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6,738 Posts
Remove the glove box. You will see the programmer behind it with a metal threaded rod attached to the top of it. With the car running change the temp display from 60 to 90 degrees. You should see this metal rod move slowly and smoothly from blend door closed (60 degrees) to open (90 degrees) If this rod is jerky as it moves or does not go the full travel, then the programmer needs replaced. You can gently unsnap this rod from the programmer lever and push it in then out to confirm the blend door isn't binding on its case. I've seen cases where this rod gets tangled in wiring as it moves or the ribbed aspirator hose just to the left of the programmer to the heater case is off or kinked at either end which will cause poor information about car interior temperature to be sent to the programmer.
 

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1926 Model T street rod, 2000 Jaguar XJ8, 1999 Corvette.
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Also the 1st thing to check when heater starts blowing cold is fluid level in a cold radiator. If low, heaters will first blow warm then cold.
 

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1990 Sedan Deville
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18 Posts
Discussion Starter #5
First thing i did check was the coolant. It's not low. This problem started when i turned the heat on and heard a loud grinding sound under the dash. Probably by the glove box. I know there was a mouse living in my car during the winter and he seemed to like my glove box. :rant2:"You Little BASTARD"!!!!! It stopped after a short while then i noticed the heat not turning on after 30 minutes of driving. I took the glove box off and checked the rod for movement and it seems to move fine. How do I get this rod off without breaking it? What do I do or check from there? :confused:
 

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1926 Model T street rod, 2000 Jaguar XJ8, 1999 Corvette.
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6,738 Posts
The rod simply pops off at the threaded end. Gently flex it out of the retainer. There are vacuum hoses at the programmers base. Mice like vacuum hoses!!
 
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