Blower Motor Circuit

Blower Motor Circuit

SYMPTOM:
- Blower motor operation is malfunctioning.

Inspection Flow:

INSPECTION FLOW

SYSTEM DESCRIPTION

Component Parts
Fan speed control system components are:
- Unified meter and A/C 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
- Fan control amp




System Operation

Automatic Mode
In the automatic mode, the blower motor speed is calculated by the unified meter and A/C amp. 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 usual automatic air flow control, starting air flow control, low water temperature starting control and high passenger compartment temperature starting control are available.

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 Usual 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 usual low speed (duty ratio 25%). During high sunload conditions, the display and unified meter and A/C amp. causes the blower speed to increase (duty ratio 49%).




Fan Speed Control Specification

COMPONENT DESCRIPTION




Fan Control Amp
The fan control amplifier is located on the cooling unit. The fan control amp. receives a gate voltage from the unified meter and A/C amp. to steplessly maintain the blower fan motor voltage in the 5 to 12 volt range (approx.).

Diagnostic Procedure For Blower Motor (Steps 1 - 3):

Diagnostic Procedure For Blower Motor (Steps 4 - 6):

Diagnostic Procedure For Blower Motor (Steps 7 - 8):

DIAGNOSTIC PROCEDURE FOR BLOWER MOTOR
SYMPTOM: Blower motor operation is malfunctioning under starting fan speed control.

COMPONENT INSPECTION




Blower Motor
Confirm smooth rotation of the blower motor.
- Ensure that there are no foreign particles inside the blower unit.