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If you're talking about on a car...........It's probably a loose vacuum hose or a broken mechanical linkage.
This is a common problem on multiple late 90's, early 00 vehicles. A lot of manufacturers went to a direct connection motor control over the blend door. Different motor schemes were used, but most suffer from a problem with the motor over-driving the blend door and breaking the plastic door over time. Once the door breaks, control over temperature in the HVAC system is lost.
HeaterTreater has developed a repair kit for multiple models using steel doors and a cheap, easy methodology for replacing the blend door. Check for additional information at www.heatertreater.net or clicking on the Google ads on this forum.
cgallen
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∙ 15y ago
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What would cause air conditioner blower to work sometimes?
Start with: Possible control, blend door or blend door actuator, low pressure switch, leak in system.
What would cause a 2000 Blazer not to change from ac to heat?
The most common problem causing a 2000 Blazer to stay on heat is a problem with the blend door. Check the blend door and its control circuit to fix the problem.
When the automatic temperature control is not maintaining the preset temperature A mechanical noise is heard in the area of the blend door What is the most likely cause?
The blend door is jammed
What would cause a 1990 GMC Sierra to have no heat?
BLEND DOOR FAILING TO MOVE TO OPEN UP HEATER CORE ACCESS.
What would cause a 1999 Jimmy to put out hot air with the htr running and then with the ac it feeds hot and cold air while running you just changed out the heater core and it was workin?
while you were doing the heater core, the controls to the blend door, or the blend door itself were moved around a bit. this would cause door not to open or close all of the way, thus presenting the problem you are dealing with right now.
What could be the cause for an automatic temperature control to stop working?
Blend door actuator failure.
What would cause the radio to stay on after the key is removed in a 2001 ford escape?
If radio goes off when door is opened - normal condition vehicle designed to operate this way Also electric windows will operate after key removed before door is opened
How to repair the blend door in the heater on a 2005 Ford Explorer?
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?
How do you repair the blend door in the heater on a 1999 Ford Windstar?
The blend door is vacuum controlled. Any vacuum leak in the engine system can cause the door to not function properly. Check this system first. The door could be physically sticking but a vacuum leak is a more common problem.
What would cause a 1999 Cougar to have no heat fan works and blend door that diverts from def vent etc works any thoughts?
a Blocked heater core
How do you replace blend door actuator on 97 ford expedition?
How do i replace blend door motor
Where is the blend door actuator for a 2005 Malibu?
Where is the blend door actuator located on a 2005 malibu
