Quest Minivan XE V6-2960cc 3.0L SOHC MFI (VG30E) (1998)
Control Assembly: Description and Operation
The EATC unit has a built-in microcomputer which processes information sent from various sensors needed for air conditioner operation. The front air
mix door motor, mode door motor, front intake door motor, front blower motor and compressor are then controlled.
The EATC unit is unitized with control mechanisms. Signals from various switches and the Temperature Control Switch are directly entered into EATC
unit.
Self-diagnostic functions are also built into EATC unit to provide a quick check of malfunctions in the auto air conditioner system.
AMBIENT TEMPERATURE INPUT PROCESS
The EATC unit includes a "processing circuit" for the ambient temperature sensor input. When a temperature increase less than -12 °C (20 °F) is
detected by the ambient temperature sensor, the "processing circuit" allows the EATC unit to recognize the temperature increase after 80 seconds
and when the temperature increase is greater than -12 °C (20 °F), 5 minutes is required.
As an example, consider stopping for a cup of coffee after high speed driving. Even though the actual ambient temperature has not changed, the
temperature detected by the ambient sensor will increase because heat radiated from the engine compartment can radiate to the front grille area
(where the ambient sensor is located).
SUNLOAD INPUT PROCESS
The EATC unit also includes a processing circuit to "average" variations in detected sunload over a period of time. This prevents drastic swings in
the EATC system operation due to small or quick variations in detected sunload.
For example, consider driving along a road bordered by an occasional group of large trees. The sunload detected by the sunload sensor will vary
whenever the trees obstruct the sunlight. The processing circuit averages the detected sunload over a period of time. The (insignificant) effect of
the trees momentarily obstructing the sunlight does not cause any change in the EATC system operation. On the other hand, shortly after entering a
long tunnel, the system will recognize the change in sunload, and the system will react accordingly.
ENGLISH/METRIC MODE
It can be accessed by simultaneously pressing the DEFROST and A/C switches and holding the blower switch in the upward position for 1 second.