Blower Motor Circuit

SYMPTOM:
- Blower motor operation is malfunctioning.

Inspection Flow:

SYSTEM DESCRIPTION

Component Parts
Fan speed control system components are:
- Auto amp.
- A/C LAN system (PBR built-in mode door motor, air mix door motor and intake 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 inputs 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.

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 A/C button 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 high sunload, the blower low speed is "normal" low speed (approx. 6 V). During low or no sunload conditions, the low speed will drop to "low" low speed (approx. 5 V ).




Fan Speed Control Specification

COMPONENT DESCRIPTION




Fan Control Amplifier
The fan control amplifier is located on the cooling unit. The fan control amp. receives a gate voltage from the auto amp. to smoothly maintain the blower fan motor voltage in the 5 to the 12 V range (approx.).

DIAGNOSTIC PROCEDURE




SYMPTOM: Blower motor operation is malfunctioning under Starting
Fan Speed Control.

Step 1:

Step 2 - 4:

Step 5 - 7:

Step 8 - 10:

COMPONENT INSPECTION




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







Fan Control Amp.
Check continuity between terminals.