got a '01 f350 lariat and the temp selector in the truck will not come off full heat

ive changed that switch panel and still the same results

truck is a diesel if that means anything

 

anyone had this problem?

 

Yeah, it could be a couple things. Could be a sticky valve, flapper, thingy. Gosh idk what to call it. Ill look up the mod to fix it. It has to do with vacuum issues.

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Here ya go. Something similar to this should fix up your issues real quick.
yet another mod done~PIC~ heater core bypass valve - Ford Truck Enthusiasts Forums
This isnt the exact "factory fix" but im sure when you are digging in around that area, you might find a valve or solenoid that is sticking cause your full heat.
Good Luck

 

Its the blend door. 30 dollar part under dash with an electric motor on it. itll take about twenty minutes to change in the dark with a screwdriver and flashlight. dont ask how i know