Blower Motor: Description and Operation

Blower Motor Circuit

SYSTEM DESCRIPTION

Component Parts
Fan speed control system components are:
- Auto amp.
- A/C LAN system (PBR built-in mode door motor and air mix door motor)
- In-vehicle sensor
- Ambient sensor
- Sunload sensor
- Intake sensor




System Operation

Automatic Mode
In the automatic mode, the blower motor speed is calculated by the automatic amplifier based on input from the PBR, in-vehicle sensor, sunload sensor, intake sensor and ambient sensor.

When the air flow is increased, the duty ratio of the blower fan motor's drive signal is changed at 8% sec. to prevent a sudden increase in air flow.

In addition to manual air flow control and the normal automatic air flow control, starting air flow control, low water temperature starting control and high passenger compartment temperature starting control are available.

When the audio-recognition signal is input to the auto amplifier, the maximum fan speed is limited to the 3rd step. (Except DEF).

Starting Fan Speed Control
Start Up From COLD SOAK Condition (Automatic mode) In a cold start up condition where the engine coolant temperature is below 56 °C (133 °F), the blower will not operate for a short period of time (up to 150 seconds). The exact start delay time varies depending on the ambient and engine coolant temperature.

In the most extreme case (very low ambient) the blower starting delay will be 150 seconds as described above. After this delay, the blower will operate at low speed until the engine coolant temperature rises above 56 °C (133 °F), at which time the blower speed will increase to the objective speed.

Start Up From Normal or HOT SOAK Condition (Automatic mode) The blower will begin operation momentarily after the AUTO switch is pushed. The blower speed will gradually rise to the objective speed over a time period of 3 seconds or less (actual time depends on the objective blower speed).

Blower Speed Compensation

Sunload
When the in-vehicle temperature and the set temperature are very close, the blower will be operating at low speed. The low speed will vary depending on the sunload. During conditions of low or no sunload, the blower low speed is normal low speed (duty ratio 25%). During high sunload conditions, the auto amp. causes the blower fan speed to increase.(duty ratio 49%).




Fan Speed Control Specification

COMPONENT DESCRIPTION




Brush-Less Motor
The blower motor utilizes a brush-less motor with a rotating magnet. Quietness is improved over previous motors where the brush was the point of contact and the coil rotated.