This is a little difficult to answer without knowing what car model we are talking about, so I'll give you a generic answer. The blend doors in modern automobiles are under computer control...not like the old slide lever with a cable attached and you move from red to blue and back. The motor is generally activated by the computer and if there is a fault in the system, the computer goes into it's "panic routine" and will usually shut the motor down to prevent further damage since it generally doesn't understand what's happening.
Typically what's happening is that the cheap plastic blend door broke and the system can no longer drive the door to a stall position and calibrate the movement range of the door. Complete computer confusion ensues since generally a full breakage was not an event foreseen by the software engineering teams. Hardware and software guys never talk and this type of occurrence is the result.
Usually the motor is good, it's the broken blend door combined with the computer fail safe algorithm that makes it look like the motor is bad. A lot of service techs will just replace the motor since that is usually easy and has a good payback instead of trying to understand and fix the problem. HeaterTreater has engineering analysis and fixes available on their web site for the most common failure models and are expanding their product portfolio. Check heatertreater.net to see if your model is listed.
it is directly below the ash tray ..under the dash..it will or should be white...with the car running.. look under this area..and turn the ac/heat knob slowly..you will see a white square box..with a metal guide going up/or down when you adjust the knob..this is the motor...if it does not move ..be sure the wire harness going to it is connected ..if it does not still move it is bad..if you have no heat..the blend door inside the ac/heat box may be damaged/broken off..or your heater core is bad..
Blend door actuator.
I do not have heat in the car and the blend door clicks. How do I access the blend door in a 2005 Ford Explorer?
Low on coolant, or stuck open thermostat, or plugged heater core, or temp blend door motor in/op.
Does your blower motor work? If it does and there is no heat the blend door actuator is probably not working and is not letting warm air into the vehicle. The blend door is staying in the cold position.
Sounds like your blend door may be broken. the blend door opens and closes on the heater core to allow heat into the cab by letting the air blow over the heater core. The heater core basically looks like a small radiator and when the blend door gets opened up, it allows to air from the blower motor to blow through the heater core fins and that heats the air before it is pushed out the vents into the cab... Check out www.heatertreater.net Those guys have videos on there of what I am talking about. It may not be your blend door though. Could also be the blend door motor or the dial to turn from cold to hot... I would check that blend door first though...
Please review the "Related Questions" below for more specific details regarding the temperature blend door and its actuator motor.
Yes, it is possible the blend door is broken in the heat position.
The blend door for a 2000 Neon is located behind the dash. The blend door controls the air flow for heat and ac.
1) blend door actuator motor has failed2) a broken blend door itselfHope it's #1 as that's cheap and easy.See "Related Questions" below for more about each
To replace a blend door on a 1999 Voyager, you will begin by checking which side of the vehicle is not receiving heat. Then, remove the glove box door by squeezing the inside of the door toward the center of the door to access the blend door.
With most heaters in vehicles the blend door mixes hot and cold air together to give you the temperature you want. Thus the name blend door