I have a 2000 Silverado Z71 5.3 L., whenever the heat is turned on you can't turn it off at all until the engine has cooled down. There is no adjustment, it's full bore all the time.
There is a part in the heating and air conditioning system called the blend door motor, this motor moves a door in the air ducts that either provides heat from the heater core or cold from the AC evaporator core, or a mix or blend of both hot and cold air, that is why it is called a blend door, the problem is the door is either stuck in the heat position or the motor that operates it has failed, this can be checked by the dealer by doing an electronic test of the systems functions, the repair is very labor intensive, since it requires removing to dash to replace the defective blend door parts.
I am a retired dealer technician and I have seen this issue many times, this is not a guess.
I did not see until your latest post comment that the fan was on high, that changes things, the AC control head may be at fault, like I said the dealer can do an electronic test of the system to determine the exact cause, only he has the correct test equip and tech manuals to resolve this problem
Continues... the blend door can still be an issue and is a common failure, changed allot of them, unless these other experts have automotive HVAC experience they are just guessing.
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It is most likely the fan speed selector for the heater motor
does the fan sjut off when the car is turned off?
if the fan is continuuisly runnig then it has nothing to do with the door bieng opened or closed
thses motors are controled by digital controls on the dash and that digital is stuck.
unplugging the battery under the hood for a while might reset the digital controls , if not then they will need to be replaced because they are failing
then that part of the control will need replacing.
have you tried unhooking the battery on the car for a while?
then the temperature control circut needs to be replaced
it is a sensor that is causing the malfunction in the temperature control
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This is issue with the fuel pump.
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this is not a fuel pump issue. this problem deals with the the heat inside the truck, you can't turn it off once its turned on.
It's not the fan speed it's the temperature control,no matter where you set it, it goes to high heat and won.t reset until the engine cools down.
I've unhooked the battery before but doesn't seem to correct the problem or change it.
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