Anyone ever had trouble with their AC switching back and forth from vent to defrost? Have an 06 f250 and bought it from a Toyota dealer, they seem to be completely stumped. Switches back and forth approx every 2-3 minutes.

 

Do you have ESOF? Does it change with engine load?

I had a similar issue with mine and it was the vacuum value solenoid had gone bad. To diagnose it I simply plugged off the ESOF line from the vacuum canister, started the engine and checked if my AC returned to normal. It did not so I checked the rest of the vacuum lines from the throttle body back and from the canister to the cabin. I found no cracks so that left the vacuum value or the canister as the issue. After checking the canister for cracks I concluded it was the value. $66 later for a new value and 5 minutes of work and my AC worked normal.

I don't know if the 05+ systems are the same but the 99-04 trucks the value is located right behind the battery.

 

Did you ever figure out your problem?

 

Had the same issue. Check this thread....

https://www.ford-trucks.com/forums/1...f-defrost.html

 

What is ESOF? Is this a picture of the vacuum value solenoid?

 

Thanks for the info! I'll see what I can do, the pic's are a big help since there are so many different components to vehicles now days.

 

Found a gray vacuum line that was off. From the time I opened the hood until the time I closed it was less than 5 minutes! And had it in the shop 3 different times!! Amazing how much people don't know or just dont put in the effort. Even though they were Toyota mechanics (because that's where we made the purchase) they should have spotted it.

Thank you all for your input it was what made the difference!