What is a blend air door motor?

Answer 1

The blend door regulates heat and AC in today's automobiles. Generally the system is set up with air always flowing through the AC evaporator coils, and the compressor is either on or off, cooling or neutral under system control. Now the air flowing through the evaporator is either directed into the vent system, or directed through the heater core and into the vent system. The blend door regulates the amount of air that is allowed to go through the heater core.

For AC, the compressor is on and the blend door blocks air flow through the heater core. For heat, the compressor is off and the blend door diverts air through the heater core. Those are the two extremes, and exacting temperature control is achieved by having the blend door in intermediate positions between the two extremes.

Remember the slide bar on the AC control panel on older cars? That slide lever was connected by cable to the blend door and temperature control was achieved by sliding the lever. On modern automobiles, that function has been transferred to computer control, using a pseudo stepper motor to control the blend door. On late 90 and early 00 cars, the motor was connected to the same plastic blend doors that were used with the slide scenario and there is a recurring problem over time with the motor being too strong and breaking the plastic blend door, leaving no control over temperature. The fix is to remove the heater box, which is a very involved operation, and replace the plastic door(which WILL break again over time).

Additional information on the cause and a cheap easy solution is available at HeaterTreater at www.heatertreater.net, or follow the Google ads on this forum.

cgallen