cant sto p the heat '01 lariat
 

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 :tu:

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 lol