Mitsubishi Electric MSH-C18TV Service Manual page 29

9-5. FAN MOTOR CONTROL
(1) Rotational frequency feedback control
The indoor fan motor is equipped with a rotational frequency sensor, and outputs signal to the microprocessor to feed
back the rotational frequency. Comparing the current rotational frequency with the target rotational frequency
(High,Med.,Low), the microprocessor controls IC141 and adjusts fan motor electric current to make the current
rotational frequency close to the target rotational frequency. With this control, when the fan speed is switched, the
rotational frequency changes smoothly.
(2) Fan motor lock-up protection
When the rotational frequency feedback signal has not output for 12 seconds, (or when the microprocessor cannot
detect the signal for 12 seconds) the fan motor is regarded locked-up. Then the electric current to the fan motor is shut
off. 3 minutes later, the electric current is applied to the fan motor again. During the fan motor lock-up, the OPERATION
INDICATOR Indicator lamp flashes on and off to show the fan motor abnormality. (Refer to page 37.)
9-6. AUTO VANE OPERATION
(1) Vane motor drive
These models are equipped with a stepping motor for the horizontal vane. The rotating direction, speed, and angle of
the motor are controlled by pulse signals (approx. 12V) transmitted from indoor microprocessor.
(2) The horizontal vane angle and mode changes as follows by pressing the VANE CONTROL button.
(3) Positioning
The vane is once pressed to the vane stopper below to confirm the standard position and then set to the desired angle.
Confirming of standard position is performed in case of follows.
(a) When the OPERATE/STOP (ON/OFF) button is pressed.
(b) When the vane control is changed from AUTO to MANUAL.
(c) When the SWING is finished.
(d) When the test run starts.
(e) When the power supply turns ON.
(4) VANE AUTO ( ) mode
In VANE AUTO mode, the microprocessor automatically determines the vane angle and operation to make the optimum
room-temperature distribution.
In COOL and DRY operation
In HEAT operation
Rotational frequency
High
Med.
High
Low
time
Vane angle is fixed to Angle 1.
Vane angle is fixed to Angle 4.
29