Blower Motor Circuit

* Automatic Air Conditioning System *

Inspection Flow (Without Navigation System):

Inspection Flow (With Navigation System):

TROUBLE DIAGNOSIS PROCEDURE FOR BLOWER MOTOR

SYSTEM DESCRIPTION

Component parts
Fan speed control system components are:
1. Auto amp.
2. Fan control amp.
3. A/C LAN system (PBR built-in air mix door motor and mode door motor)
4. In-vehicle sensor
5. Ambient sensor
6. Sunload sensor
7. 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. The blower motor applied voltage ranges from approximately 5 volts (lowest speed) to 12 volts (highest speed).

The control blower speed (in the range of 5 to 12 V), the automatic amplifier supplies a gate voltage to the fan control amplifier. Based on this voltage, the fan control amplifier controls the voltage supplied to the blower motor.

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 50 °C (122 °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 126 seconds as described above. After this delay, the blower will operate at low speed until the engine coolant temperature rises above 55 °C (131 °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 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 / Auto A/C:

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 steplessly maintain the blower fan motor voltage in the 5 to 12 volt range (approx.).