Just set the temperature and the vehicle stays comfortable.  Climate control technology is usually taken for granted, until something goes wrong.  When it does, the cost can be quite surprising.

Climate control in modern vehicles is a quite complex system.  Small computerized motors, called actuators move doors to control the functions.  An actuator is a small computer, with a reversible motor, gear drive system and a position sensor built into one unit.

The final drive gear attaches to one of a series of doors.  It also contains a sensor that monitors the position of the door.  This sensor reports the door position.  The information is sent to the temperature control computer by one of the internal networks.  The computer can then vary the position of the various doors to control temperature and air flow.

The mode actuator controls the position from which air will blow (e.g., vent, floor or defrost)

The blend actuator controls the blending of warm and cold air.  Dual zone system may have two or more blend actuators.

The fresh/circulate actuator controls inside and outside air used in the system. Sometimes alos called fresh air re-circulate.

A Heater control actuator can control heater flow.  On some systems this is controlled by the mode actuator.

Some vehicles also have individual right and left temperature actuators.  This allows individual temperature selection from side to side.

When maximum cooling is requested, the fresh/circulate actuator moves to circulate.  This allows the air inside the vehicle to be used.  Since this air inside is generally cooler than outside air and already dehumidified, cooling is greatly enhanced.  The blend door closes off flow to the heater core and the mode door moves to the panel position.  Cold air flows from the vents.

If the air gets too cold, the blend door can open slightly, allowing the air to reheat to the desired temperature.  When heating is requested, the blend door will direct air flow through the heater core.  The mode and/or heater actuators may also direct air to the floor.

Each door can operate independently of the others to achieve almost any effect desired.  Unfortunately, with such a complex system, a lot can fail.  The actuators sometimes fail, the doors can stick and also break.  When this happens, the dash must sometimes be removed to repair the situation.

Ford has been particularly prone to this problem.  The plastic blend door shaft tends to fracture.  This can keep the door from sealing off the heater core.  The effect is the air conditioner does not get cool.

Properly diagnosed, the problem is bad enough.  Remove the dash and replace the blend door.  All too often, the problem is mis-diagnosed.  The air conditioner does not get cold, so more refrigerant is added to the system.  This does not help the problem and instead over-charges the system and destroys the compressor.  The vehicle owner now has two very expensive problems, instead of one.

   Heater and/or air conditioner does not work

  The air conditioner is not as cool as before

  The heater does not blow as hot as before

  Heater or air conditioner is erratic

  Noises from under the dash

  The system does not respond to commands

With climate control, proper diagnosis and repair are the keys to lower cost.  When the air conditioner or heater stop working or work erratically, bring your vehicle to the professionals at AGCO.  We understand temperature control systems and can properly diagnose and repair them.  Quality diagnosis and repair, it cost a lot less.