'99 Exp. My AC blows cold most of the time when I first start the car, after awhile it begins to blow hot (heater hot). If I mess with the switches for awhile it will blow cold again at least for a little while. It appears to work fine at highway speeds, but if I stop for a light, it starts to blow hot again as soon as I take off. You can hear a flap close (or open) sometimes when you move the switches. I have read several post concerning the blend door, but I don't know how to check to see if this is the problem. According to my manual, I have to take apart the dash to get to the blend door. Is that correct? I would hate to go through all of that only to find out it is something else.
Thanks for any help you can provide.

 

Automatic or manual controls? Any unexpected changes in the airflow, like from where you have it set it just up and changes to defrost on its own?

 

It has manual controls. If the AC is set on and you start the car it works fine until you come to a stop. As you take off sometimes it starts blowing hot air out the AC vents. It's not room tempature but HOT air. If you turn the switch to defrost and then off and then back to AC, it sometimes goes back to cold. You may have to switch it back and forth several times to get it to work. If you turn off the car and let it sit for a minute or two it usually will blow cold when you restart the car. Thanks.

 

I have a 99 f150 and the dash had to come apart to get to the blend door. My AC did the same thing you are describing and when it got cold out I realized the heater didn't get very warm. Turned out the hinge on the blend door...where it goes into the turning actuator...was broken. After fixing it both the heat and AC came back to life. I'm not really sure about your dash...according to blend door fixes that I've seen for expeditions you can get to it by removing the glove box.Good Luck!

 

Sounds like you have vacum leak or a bad vacum switch

 

Might also be a leaking vaccuum reservoir, seeing as how it happens when you first take off from a stop.

Steve

 

My 1978 F350 AC Is working, bubut the temperature coming from the vents does not seem cool enough. What should the tempature be coming out of the vents?